Biochimica et Biophysica Acta (BBA) - Biomembranes, 2003
While the zebrafish is commonly used for studies of developmental biology and toxicology, very li... more While the zebrafish is commonly used for studies of developmental biology and toxicology, very little is known about their osmoregulatory physiology. The present investigation of Na + and Cl À transport revealed that the zebrafish is able to tolerate extremely low ambient ion concentrations and that this is achieved at least in part by a greatly enhanced apparent uptake capacity and affinity for both ions. Zebrafish maintain plasma and whole body electrolyte concentrations similar to most other freshwater teleosts even in deionized water containing only 35 AM NaCl, i.e soft water. We recorded an extremely low transport affinity constant (K m ) of 8 F 1 AM for the active uptake of Cl À in soft water acclimated fish, while other transport kinetic parameters were in agreement with reports for other freshwater organisms. While both Na + and Cl À uptake in soft water clearly depends on apical proton pump activity, changes in abundance and possibly localization of this protein did not appear to contribute to soft water acclimation. Active Cl À uptake was strongly dependent on branchial carbonic anhydrase (CA) activity regardless of water type, while the response of Na + transport to a CA inhibitor was more variable. Differential response of Na + uptake to amiloride depending on acclimation medium suggests that different Na + transport mechanisms are employed by zebrafish acclimated to soft and hard water.
American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 2015
The guanylin family of peptides are effective regulators of intestinal physiology in marine teleo... more The guanylin family of peptides are effective regulators of intestinal physiology in marine teleosts. In the distal intestinal segments, they inhibit or reverse fluid absorption by inhibiting the absorptive short-circuit current (ISC). The present findings demonstrate that mRNA from guanylin (GN) and uroguanylin (UGN), as well as at least one isoform of the guanylin peptide receptor, apical guanylyl cyclase-C (GC-C), was highly expressed in the intestine and rectum of the Gulf toadfish (Opsanus beta). In the posterior intestine, GC-C, as well as the cystic fibrosis transmembrane conductance regulator (CFTR) and basolateral Na(+)/K(+)/2Cl(-)-cotransporter (NKCC1), which comprise a Cl(-)-secretory pathway, were transcriptionally upregulated in 60 ppt. The present study also shows that, in intestinal tissues from Gulf toadfish held in 35 ppt, renoguanylin (RGN) expectedly causes net Cl(-) secretion, inhibits both the absorptive ISC and fluid absorption, and decreases HCO3 (-) secretion. Likewise, in intestinal tissues from Gulf toadfish acclimated to 60 ppt, RGN also inhibits the absorptive I ISC and fluid absorption, but to an even greater extent, corresponding with the mRNA expression data. In contrast, RGN does not alter Cl(-) flux and, instead, elevates HCO3 (-) secretion in the 60 ppt group, suggesting increased apical Cl(-)/HCO3 (-) exchange activity by SLC26a6. Overall, these findings reinforce the hypotheses that the guanylin peptide system is important for salinity acclimatization and that the secretory response could facilitate the removal of solids, such as CaCO3 precipitates, from the intestine.
Atlantic salmon Salmo salar smolts were exposed to one of the four different aerobic exercise reg... more Atlantic salmon Salmo salar smolts were exposed to one of the four different aerobic exercise regimens for 10 weeks followed by a 1 week final smoltification period in fresh water and a subsequent eight-day seawater transfer period. Samples of gill and intestinal tissue were taken at each time point and gene expression was used to assess the effects of exercise training on both branchial and intestinal osmoregulatory pathways. Real-time polymerase chain reaction (PCR) analysis revealed that exercise training up-regulated the expression of seawater relevant genes in the gills of S. salar smolts, including Na(+) , K(+) ATPase (nka) subunit α1b, the Na(+) , K(+) , 2 Cl(-) co-transporter (nkcc1) and cftr channel. These findings suggest that aerobic exercise stimulates expression of seawater ion transport pathways that may act to shift the seawater transfer window for S. salar smolts. Aerobic exercise also appeared to stimulate freshwater ion uptake mechanisms probably associated with an...
American journal of physiology. Regulatory, integrative and comparative physiology, 2014
The physiological effects of guanylin (GN) and uroguanylin (UGN) on fluid and electrolyte transpo... more The physiological effects of guanylin (GN) and uroguanylin (UGN) on fluid and electrolyte transport in the teleost fish intestine have yet to be thoroughly investigated. In the present study, the effects of GN, UGN, and renoguanylin (RGN; a GN and UGN homolog) on short-circuit current (Isc) and the transport of Cl-, Na+, bicarbonate (HCO3-), and fluid in the Gulf toadfish (Opsanus beta) intestine were determined using Ussing chambers, pH-stat titration, and intestinal sac experiments. GN, UGN, and RGN reversed the Isc of the posterior intestine (absorptive-to-secretory), but not of the anterior intestine. RGN decreased baseline HCO3- secretion, but increased Cl- and fluid secretion in the posterior intestine. The secretory response of the posterior intestine coincides with the presence of basolateral NKCC1 and apical cystic fibrosis transmembrane conductance regulator (CFTR), the latter of which is lacking in the anterior intestine and is not permeable to HCO3- in the posterior inte...
The article discusses advances in osmoregulation and excretion with emphasis on how multicellular... more The article discusses advances in osmoregulation and excretion with emphasis on how multicellular animals in different osmotic environments regulate their milieu intérieur. Mechanisms of energy transformations in animal osmoregulation are dealt with in biophysical terms with respect to water and ion exchange across biological membranes and coupling of ion and water fluxes across epithelia. The discussion of functions is based on a comparative approach analyzing mechanisms that have evolved in different taxonomic groups at biochemical, cellular and tissue levels and their integration in maintaining whole body water and ion homeostasis. The focus is on recent studies of adaptations and newly discovered mechanisms of acclimatization during transitions of animals between different osmotic environments. Special attention is paid to hypotheses about the diversity of cellular organization of osmoregulatory and excretory organs such as glomerular kidneys, antennal glands, Malpighian tubules and insect gut, gills, integument and intestine, with accounts on experimental approaches and methods applied in the studies. It is demonstrated how knowledge in these areas of comparative physiology has expanded considerably during the last two decades, bridging seminal classical works with studies based on new approaches at all levels of anatomical and functional organization. A number of as yet partially unanswered questions are emphasized, some of which are about how water and solute exchange mechanisms at lower levels are integrated for regulating whole body extracellular water volume and ion homeostasis of animals in their natural habitats. C 2014 American Physiological Society.
Influence of water Ag(I) speciation on pharmacokinetics of Ag(I) during a post-exposure period wa... more Influence of water Ag(I) speciation on pharmacokinetics of Ag(I) during a post-exposure period was investigated in rainbow trout (Oncorhynchus mykiss ) and European eel (Anguilla anguilla ). The rainbow trout is sensitive to waterborne ionic Ag ' whereas the eel is tolerant. The fish were acclimated to either of two chloride concentrations, 10 or 1200 mM, in synthetic soft water and then exposed to a sublethal 24-h pulse of 1.3 mg l (1 of 110m Ag(I) added as 110m AgNO 3 in these waters. The protocol provided exposures to mainly the free ion Ag ' (low chloride water) or mainly AgCl aq (high chloride water). Contents and concentrations of 110m Ag(I) in tissues and body fluids were then monitored over a 67-day post-exposure period in Ag(I)-free water of the same chloride levels. Changing the speciation of Ag(I) in the water had no effect on the whole body load of 110m Ag(I), but did result in differences in internal distribution. In trout, changing water Ag(I) speciation significantly altered elimination or accumulation of Ag(I) in several body compartments. Notably, trout exposed to AgCl aq eliminated 110m Ag(I) from the kidney more quickly than trout exposed to Ag(I) primarily as Ag ' . This elimination was matched by higher concentrations of 110m Ag in liver of trout exposed to Ag(I) primarily as AgCl aq . In eel, shifting speciation from Ag ' to AgCl aq hastened elimination of 110m Ag(I) from mid and posterior intestine and increased 110m Ag(I) retention in kidney. While there was no difference between the two fish species in whole body 110m Ag(I) load, most internal body compartments of trout had higher 110m Ag(I) concentrations than those in eel early in the experiment. Because tissue-specific elimination times were longer in eel than in trout, these differences were generally cancelled by the end of the 67-day depuration period. The only exception was the liver, which in trout continued to accumulate 110m Ag(I) throughout the experiment but in eel remained unchanged. The combined effect of 110m Ag(I) movements in the two species was that trout retained all their accumulated 110m Ag(I) through the 67-day period, whereas the body burden of 110m Ag(I) in eel was reduced to half initial values by day 67. # (C. Hogstrand). Aquatic Toxicology 63 (2003) 139 Á/157 www.elsevier.com/locate/aquatox 0166-445X/02/$ -see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 6 -4 4 5 X ( 0 2 ) 0 0 1 7 4 -1
Interest in culturing the Pacific white shrimp Litopenaeus vannamei in low-salinity and brackish-... more Interest in culturing the Pacific white shrimp Litopenaeus vannamei in low-salinity and brackish-well waters has led to questions about the ability of this species to osmo-and ionoregulate in environments containing low concentrations of ions and in environments with ionic ratios that differ from those found in sea water. After seven days, hemolymph osmolality and potassium, sodium and calcium values were all significantly affected by salinity (as artificial sea salt) with values decreasing with decreasing salinity. These decreases were small, however, relative to decreases in salinity, indicating iono-and osmoregulation with adjustment for gradients. The hemolymph osmolality and sodium and calcium concentrations in shrimp exposed to either 2 g/L artificial sea salt or 2 g/L mixed-ion solution (a mixture of sodium, potassium, calcium, and magnesium chlorides that approximate the concentrations and ratios of these cations found in 2 g/L dilute seawater) did not differ significantly. However, hemolymph potassium levels were significantly lower in shrimp held in the mixed-ion environment. Potassium influx rates were similar in shrimp held in either artificial sea salt or mixed ions. The results of this study indicate that salinity affects hemolymph-cation concentrations and osmolality. Further, differential potassium-influx rates do not appear to be the basis for low hemolymph potassium levels observed in shrimp held in mixed-ion environments.
The Deepwater Horizon incident likely resulted in exposure of commercially and ecologically impor... more The Deepwater Horizon incident likely resulted in exposure of commercially and ecologically important fish species to crude oil during the sensitive early life stages. We show that brief exposure of a water-accommodated fraction of oil from the spill to mahi-mahi as juveniles, or as embryos/larvae that were then raised for ∼25 days to juveniles, reduces their swimming performance. These physiological deficits, likely attributable to polycyclic aromatic hydrocarbons (PAHs), occurred at environmentally realistic exposure concentrations. Specifically, a 48 h exposure of 1.2 ± 0.6 μg L(-1) ΣPAHs (geometric mean ± SEM) to embryos/larvae that were then raised to juvenile stage or a 24 h exposure of 30 ± 7 μg L(-1) ΣPAHs (geometric mean ± SEM) directly to juveniles resulted in 37% and 22% decreases in critical swimming velocities (Ucrit), respectively. Oil-exposed larvae from the 48 h exposure showed a 4.5-fold increase in the incidence of pericardial and yolk sac edema relative to control...
Cultured branchial cell epithelia from freshwater rainbow trout were incubated with ((32)P)phosph... more Cultured branchial cell epithelia from freshwater rainbow trout were incubated with ((32)P)phosphate and ((14)C)acetate as lipid precursors under both symmetrical (L15 media apical/L15 media basolateral) and asymmetrical (freshwater apical/L15 media basolateral) culture conditions. Epithelia composed of pavement cells alone, or containing both pavement cells and chloride cells, were examined. Lipids (labeled with (32)P and (14)C) were isolated and assayed by thinlayer chromatography, and fatty acids (labeled with (14)C) were isolated and assayed by paper chromatography. The main goal was to see whether the loss of a major incorporation into ((32)P)phosphatidylethanolamine [((32)P)PE], previously seen in eel gills in vivo when the fish were transferred from an osmotic steady state to more dilute media, was the result of a hormonal regulation, i.e., did it only apply to gill tissue in vivo or could it also be seen in the absence of hormonal modulation after incorporation of ((32)P)pho...
The article discusses advances in osmoregulation and excretion with emphasis on how multicellular... more The article discusses advances in osmoregulation and excretion with emphasis on how multicellular animals in different osmotic environments regulate their milieu intérieur. Mechanisms of energy transformations in animal osmoregulation are dealt with in biophysical terms with respect to water and ion exchange across biological membranes and coupling of ion and water fluxes across epithelia. The discussion of functions is based on a comparative approach analyzing mechanisms that have evolved in different taxonomic groups at biochemical, cellular and tissue levels and their integration in maintaining whole body water and ion homeostasis. The focus is on recent studies of adaptations and newly discovered mechanisms of acclimatization during transitions of animals between different osmotic environments. Special attention is paid to hypotheses about the diversity of cellular organization of osmoregulatory and excretory organs such as glomerular kidneys, antennal glands, Malpighian tubules and insect gut, gills, integument and intestine, with accounts on experimental approaches and methods applied in the studies. It is demonstrated how knowledge in these areas of comparative physiology has expanded considerably during the last two decades, bridging seminal classical works with studies based on new approaches at all levels of anatomical and functional organization. A number of as yet partially unanswered questions are emphasized, some of which are about how water and solute exchange mechanisms at lower levels are integrated for regulating whole body extracellular water volume and ion homeostasis of animals in their natural habitats. C 2014 American Physiological Society.
Physiological mechanisms of silver toxicity (as silver nitrate) to the sensitive rainbow trout (O... more Physiological mechanisms of silver toxicity (as silver nitrate) to the sensitive rainbow trout (Oncorhynchus mykiss) (96 h LC50: 10.2 μg silver l−1, in soft, low chloride water) and the more tolerant European eel (Anguilla anguilla)(96 h LC50: 34.4 μg silver l−1, in the same water) were investigated during acute exposure to silver, using concentrations varying from 3 to 22 μg
Adult rainbow trout were pre-exposed to a sublethal concentration of waterborne cadmium (Cd, 26.7... more Adult rainbow trout were pre-exposed to a sublethal concentration of waterborne cadmium (Cd, 26.7 nmol/l) or waterborne zinc (Zn, 2294 nmol/l) for 30 days to induce acclimation. A single dose of radiolabeled Cd (64.4 nmol/kg) or Zn (183.8 nmol/kg) was injected into the vascular system of non-acclimated and Cd- or Zn-acclimated trout through indwelling arterial catheters. Subsequently, repetitive blood samples over 10 h and terminal tissue samples (liver, heart, bile, stomach, intestine, kidney, gills, muscle, and spleen) were taken to characterize the effect of metal acclimation on clearance kinetics in vivo. Plasma clearance of Cd in Cd-acclimated fish (0.726±0.015 and 0.477±0.012 ml/min per kg for total and newly accumulated Cd, respectively), was faster than that in non-acclimated trout (0.493±0.013 and 0.394±0.009 ml/min per kg). Unlike plasma Cd, the levels of Cd in red blood cells (RBCs) were 1.2–2.2 times higher in Cd-acclimated fish than in non-acclimated fish. At 10 h post-...
However, thermal change can alter lobster acid-base status over a time course of minutes. Acute i... more However, thermal change can alter lobster acid-base status over a time course of minutes. Acute increases in temperature trigger a respiratory compensated metabolic acidosis of the hemolymph. Both the strength and frequency of the lobster heartbeat in vitro are modulated by changes in pH within the physiological range measured in vivo. These observations suggest that changes in acid-base status triggered by thermal variations in the environment might modulate lobster cardiac performance in vivo.
It is well established that serotonin (5-HT; 5-hydroxytryptamine) plays a role in mammalian regul... more It is well established that serotonin (5-HT; 5-hydroxytryptamine) plays a role in mammalian regulation of the hypothalamic-pituitary-adrenal (HPA) axis via the 5-HT receptor subtype 1A (5-HT 1A ). To date, there has not been a comprehensive investigation of the molecular, pharmacological and physiological aspects of the 5-HT 1A receptor and its role in the activation of the hypothalamic-pituitary-interrenal (HPI) axis in teleost fish. The 5-HT 1A receptor of the Gulf toadfish (Opsanus beta) was cloned and sequenced, showing 67.5% amino acid similarity to the human homologue. The 5-HT 1A receptor was distributed throughout the brain, with the whole brain containing significantly higher levels of 5-HT 1A mRNA compared to all other tissues and the midbrain/diencephalon region containing significantly higher levels of transcript than any other brain region. Substantial levels of transcript were also found in the pituitary, while very low levels were in the kidney that contains the interrenal cells. Xenopus oocytes injected with toadfish 5-HT 1A receptor cRNA displayed significantly higher binding of [ 3 H]5-HT that was abolished by the mammalian 5-HT 1A receptor agonist, 8-OH-DPAT, indicating a conserved binding site of the toadfish 5-HT 1A receptor and a high specificity for the agonist. Supporting this, binding of [ 3 H]5-HT was not affected by the mammalian 5-HT 1B receptor agonist, 5-nonyloxytryptamine, the 5-HT 7 receptor antagonist, SB269970, or the 5-HT 2 receptor agonist, a-methylserotonin. Confirming these molecular and pharmacological findings, intravenous injection of 8-OH-DPAT stimulated the HPI axis to cause a 2-fold increase in circulating levels of cortisol. The present study of the 5-HT 1A receptor in a single teleost species illustrates the high conservation of this 5-HT receptor amongst vertebrates.
Adult crayfish (Cambarus diogenes diogenes) exposed to 8.41 Ϯ 0.17 g silver/L (19.4% as Ag ϩ ) in... more Adult crayfish (Cambarus diogenes diogenes) exposed to 8.41 Ϯ 0.17 g silver/L (19.4% as Ag ϩ ) in moderately hard freshwater under flow-through conditions for 96 h exhibited ionoregulatory disturbance, elevated metabolic ammonia (T amm ) production and substantial silver accumulation in the gills, hemolymph, and hepatopancreas. The ionoregulatory disturbance included both a generally reduced unidirectional Na ϩ influx and an increased unidirectional Na ϩ efflux, leading to a substantial net loss of Na ϩ from the silver-exposed crayfish. The Na ϩ uptake in silver-exposed crayfish differed overall from controls, while the increased Na ϩ efflux recovered to control values 48 h into the 96 h of exposure. The general inhibition of Na ϩ uptake could be explained by a reduced sodium/potassium-adenosine triphosphatase (Na/K-ATPase) activity in terminally obtained gill samples from the silverexposed crayfish. The silver-induced effect on Na ϩ uptake and loss translated to reduced hemolymph Na ϩ concentrations but not significantly reduced hemolymph Cl Ϫ concentrations. Hemolymph T amm and T amm efflux both increased in silver-exposed crayfish, indicating an increased metabolic T amm production. The present study demonstrates that the toxic mechanism of waterborne silver exposure in freshwater crayfish resembles that of freshwater teleost fish. The crayfish might therefore be a useful model system for extending current environmental regulatory strategies, currently based on teleost fish, to invertebrates.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2003
While the zebrafish is commonly used for studies of developmental biology and toxicology, very li... more While the zebrafish is commonly used for studies of developmental biology and toxicology, very little is known about their osmoregulatory physiology. The present investigation of Na + and Cl À transport revealed that the zebrafish is able to tolerate extremely low ambient ion concentrations and that this is achieved at least in part by a greatly enhanced apparent uptake capacity and affinity for both ions. Zebrafish maintain plasma and whole body electrolyte concentrations similar to most other freshwater teleosts even in deionized water containing only 35 AM NaCl, i.e soft water. We recorded an extremely low transport affinity constant (K m ) of 8 F 1 AM for the active uptake of Cl À in soft water acclimated fish, while other transport kinetic parameters were in agreement with reports for other freshwater organisms. While both Na + and Cl À uptake in soft water clearly depends on apical proton pump activity, changes in abundance and possibly localization of this protein did not appear to contribute to soft water acclimation. Active Cl À uptake was strongly dependent on branchial carbonic anhydrase (CA) activity regardless of water type, while the response of Na + transport to a CA inhibitor was more variable. Differential response of Na + uptake to amiloride depending on acclimation medium suggests that different Na + transport mechanisms are employed by zebrafish acclimated to soft and hard water.
American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 2015
The guanylin family of peptides are effective regulators of intestinal physiology in marine teleo... more The guanylin family of peptides are effective regulators of intestinal physiology in marine teleosts. In the distal intestinal segments, they inhibit or reverse fluid absorption by inhibiting the absorptive short-circuit current (ISC). The present findings demonstrate that mRNA from guanylin (GN) and uroguanylin (UGN), as well as at least one isoform of the guanylin peptide receptor, apical guanylyl cyclase-C (GC-C), was highly expressed in the intestine and rectum of the Gulf toadfish (Opsanus beta). In the posterior intestine, GC-C, as well as the cystic fibrosis transmembrane conductance regulator (CFTR) and basolateral Na(+)/K(+)/2Cl(-)-cotransporter (NKCC1), which comprise a Cl(-)-secretory pathway, were transcriptionally upregulated in 60 ppt. The present study also shows that, in intestinal tissues from Gulf toadfish held in 35 ppt, renoguanylin (RGN) expectedly causes net Cl(-) secretion, inhibits both the absorptive ISC and fluid absorption, and decreases HCO3 (-) secretion. Likewise, in intestinal tissues from Gulf toadfish acclimated to 60 ppt, RGN also inhibits the absorptive I ISC and fluid absorption, but to an even greater extent, corresponding with the mRNA expression data. In contrast, RGN does not alter Cl(-) flux and, instead, elevates HCO3 (-) secretion in the 60 ppt group, suggesting increased apical Cl(-)/HCO3 (-) exchange activity by SLC26a6. Overall, these findings reinforce the hypotheses that the guanylin peptide system is important for salinity acclimatization and that the secretory response could facilitate the removal of solids, such as CaCO3 precipitates, from the intestine.
Atlantic salmon Salmo salar smolts were exposed to one of the four different aerobic exercise reg... more Atlantic salmon Salmo salar smolts were exposed to one of the four different aerobic exercise regimens for 10 weeks followed by a 1 week final smoltification period in fresh water and a subsequent eight-day seawater transfer period. Samples of gill and intestinal tissue were taken at each time point and gene expression was used to assess the effects of exercise training on both branchial and intestinal osmoregulatory pathways. Real-time polymerase chain reaction (PCR) analysis revealed that exercise training up-regulated the expression of seawater relevant genes in the gills of S. salar smolts, including Na(+) , K(+) ATPase (nka) subunit α1b, the Na(+) , K(+) , 2 Cl(-) co-transporter (nkcc1) and cftr channel. These findings suggest that aerobic exercise stimulates expression of seawater ion transport pathways that may act to shift the seawater transfer window for S. salar smolts. Aerobic exercise also appeared to stimulate freshwater ion uptake mechanisms probably associated with an...
American journal of physiology. Regulatory, integrative and comparative physiology, 2014
The physiological effects of guanylin (GN) and uroguanylin (UGN) on fluid and electrolyte transpo... more The physiological effects of guanylin (GN) and uroguanylin (UGN) on fluid and electrolyte transport in the teleost fish intestine have yet to be thoroughly investigated. In the present study, the effects of GN, UGN, and renoguanylin (RGN; a GN and UGN homolog) on short-circuit current (Isc) and the transport of Cl-, Na+, bicarbonate (HCO3-), and fluid in the Gulf toadfish (Opsanus beta) intestine were determined using Ussing chambers, pH-stat titration, and intestinal sac experiments. GN, UGN, and RGN reversed the Isc of the posterior intestine (absorptive-to-secretory), but not of the anterior intestine. RGN decreased baseline HCO3- secretion, but increased Cl- and fluid secretion in the posterior intestine. The secretory response of the posterior intestine coincides with the presence of basolateral NKCC1 and apical cystic fibrosis transmembrane conductance regulator (CFTR), the latter of which is lacking in the anterior intestine and is not permeable to HCO3- in the posterior inte...
The article discusses advances in osmoregulation and excretion with emphasis on how multicellular... more The article discusses advances in osmoregulation and excretion with emphasis on how multicellular animals in different osmotic environments regulate their milieu intérieur. Mechanisms of energy transformations in animal osmoregulation are dealt with in biophysical terms with respect to water and ion exchange across biological membranes and coupling of ion and water fluxes across epithelia. The discussion of functions is based on a comparative approach analyzing mechanisms that have evolved in different taxonomic groups at biochemical, cellular and tissue levels and their integration in maintaining whole body water and ion homeostasis. The focus is on recent studies of adaptations and newly discovered mechanisms of acclimatization during transitions of animals between different osmotic environments. Special attention is paid to hypotheses about the diversity of cellular organization of osmoregulatory and excretory organs such as glomerular kidneys, antennal glands, Malpighian tubules and insect gut, gills, integument and intestine, with accounts on experimental approaches and methods applied in the studies. It is demonstrated how knowledge in these areas of comparative physiology has expanded considerably during the last two decades, bridging seminal classical works with studies based on new approaches at all levels of anatomical and functional organization. A number of as yet partially unanswered questions are emphasized, some of which are about how water and solute exchange mechanisms at lower levels are integrated for regulating whole body extracellular water volume and ion homeostasis of animals in their natural habitats. C 2014 American Physiological Society.
Influence of water Ag(I) speciation on pharmacokinetics of Ag(I) during a post-exposure period wa... more Influence of water Ag(I) speciation on pharmacokinetics of Ag(I) during a post-exposure period was investigated in rainbow trout (Oncorhynchus mykiss ) and European eel (Anguilla anguilla ). The rainbow trout is sensitive to waterborne ionic Ag ' whereas the eel is tolerant. The fish were acclimated to either of two chloride concentrations, 10 or 1200 mM, in synthetic soft water and then exposed to a sublethal 24-h pulse of 1.3 mg l (1 of 110m Ag(I) added as 110m AgNO 3 in these waters. The protocol provided exposures to mainly the free ion Ag ' (low chloride water) or mainly AgCl aq (high chloride water). Contents and concentrations of 110m Ag(I) in tissues and body fluids were then monitored over a 67-day post-exposure period in Ag(I)-free water of the same chloride levels. Changing the speciation of Ag(I) in the water had no effect on the whole body load of 110m Ag(I), but did result in differences in internal distribution. In trout, changing water Ag(I) speciation significantly altered elimination or accumulation of Ag(I) in several body compartments. Notably, trout exposed to AgCl aq eliminated 110m Ag(I) from the kidney more quickly than trout exposed to Ag(I) primarily as Ag ' . This elimination was matched by higher concentrations of 110m Ag in liver of trout exposed to Ag(I) primarily as AgCl aq . In eel, shifting speciation from Ag ' to AgCl aq hastened elimination of 110m Ag(I) from mid and posterior intestine and increased 110m Ag(I) retention in kidney. While there was no difference between the two fish species in whole body 110m Ag(I) load, most internal body compartments of trout had higher 110m Ag(I) concentrations than those in eel early in the experiment. Because tissue-specific elimination times were longer in eel than in trout, these differences were generally cancelled by the end of the 67-day depuration period. The only exception was the liver, which in trout continued to accumulate 110m Ag(I) throughout the experiment but in eel remained unchanged. The combined effect of 110m Ag(I) movements in the two species was that trout retained all their accumulated 110m Ag(I) through the 67-day period, whereas the body burden of 110m Ag(I) in eel was reduced to half initial values by day 67. # (C. Hogstrand). Aquatic Toxicology 63 (2003) 139 Á/157 www.elsevier.com/locate/aquatox 0166-445X/02/$ -see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 6 -4 4 5 X ( 0 2 ) 0 0 1 7 4 -1
Interest in culturing the Pacific white shrimp Litopenaeus vannamei in low-salinity and brackish-... more Interest in culturing the Pacific white shrimp Litopenaeus vannamei in low-salinity and brackish-well waters has led to questions about the ability of this species to osmo-and ionoregulate in environments containing low concentrations of ions and in environments with ionic ratios that differ from those found in sea water. After seven days, hemolymph osmolality and potassium, sodium and calcium values were all significantly affected by salinity (as artificial sea salt) with values decreasing with decreasing salinity. These decreases were small, however, relative to decreases in salinity, indicating iono-and osmoregulation with adjustment for gradients. The hemolymph osmolality and sodium and calcium concentrations in shrimp exposed to either 2 g/L artificial sea salt or 2 g/L mixed-ion solution (a mixture of sodium, potassium, calcium, and magnesium chlorides that approximate the concentrations and ratios of these cations found in 2 g/L dilute seawater) did not differ significantly. However, hemolymph potassium levels were significantly lower in shrimp held in the mixed-ion environment. Potassium influx rates were similar in shrimp held in either artificial sea salt or mixed ions. The results of this study indicate that salinity affects hemolymph-cation concentrations and osmolality. Further, differential potassium-influx rates do not appear to be the basis for low hemolymph potassium levels observed in shrimp held in mixed-ion environments.
The Deepwater Horizon incident likely resulted in exposure of commercially and ecologically impor... more The Deepwater Horizon incident likely resulted in exposure of commercially and ecologically important fish species to crude oil during the sensitive early life stages. We show that brief exposure of a water-accommodated fraction of oil from the spill to mahi-mahi as juveniles, or as embryos/larvae that were then raised for ∼25 days to juveniles, reduces their swimming performance. These physiological deficits, likely attributable to polycyclic aromatic hydrocarbons (PAHs), occurred at environmentally realistic exposure concentrations. Specifically, a 48 h exposure of 1.2 ± 0.6 μg L(-1) ΣPAHs (geometric mean ± SEM) to embryos/larvae that were then raised to juvenile stage or a 24 h exposure of 30 ± 7 μg L(-1) ΣPAHs (geometric mean ± SEM) directly to juveniles resulted in 37% and 22% decreases in critical swimming velocities (Ucrit), respectively. Oil-exposed larvae from the 48 h exposure showed a 4.5-fold increase in the incidence of pericardial and yolk sac edema relative to control...
Cultured branchial cell epithelia from freshwater rainbow trout were incubated with ((32)P)phosph... more Cultured branchial cell epithelia from freshwater rainbow trout were incubated with ((32)P)phosphate and ((14)C)acetate as lipid precursors under both symmetrical (L15 media apical/L15 media basolateral) and asymmetrical (freshwater apical/L15 media basolateral) culture conditions. Epithelia composed of pavement cells alone, or containing both pavement cells and chloride cells, were examined. Lipids (labeled with (32)P and (14)C) were isolated and assayed by thinlayer chromatography, and fatty acids (labeled with (14)C) were isolated and assayed by paper chromatography. The main goal was to see whether the loss of a major incorporation into ((32)P)phosphatidylethanolamine [((32)P)PE], previously seen in eel gills in vivo when the fish were transferred from an osmotic steady state to more dilute media, was the result of a hormonal regulation, i.e., did it only apply to gill tissue in vivo or could it also be seen in the absence of hormonal modulation after incorporation of ((32)P)pho...
The article discusses advances in osmoregulation and excretion with emphasis on how multicellular... more The article discusses advances in osmoregulation and excretion with emphasis on how multicellular animals in different osmotic environments regulate their milieu intérieur. Mechanisms of energy transformations in animal osmoregulation are dealt with in biophysical terms with respect to water and ion exchange across biological membranes and coupling of ion and water fluxes across epithelia. The discussion of functions is based on a comparative approach analyzing mechanisms that have evolved in different taxonomic groups at biochemical, cellular and tissue levels and their integration in maintaining whole body water and ion homeostasis. The focus is on recent studies of adaptations and newly discovered mechanisms of acclimatization during transitions of animals between different osmotic environments. Special attention is paid to hypotheses about the diversity of cellular organization of osmoregulatory and excretory organs such as glomerular kidneys, antennal glands, Malpighian tubules and insect gut, gills, integument and intestine, with accounts on experimental approaches and methods applied in the studies. It is demonstrated how knowledge in these areas of comparative physiology has expanded considerably during the last two decades, bridging seminal classical works with studies based on new approaches at all levels of anatomical and functional organization. A number of as yet partially unanswered questions are emphasized, some of which are about how water and solute exchange mechanisms at lower levels are integrated for regulating whole body extracellular water volume and ion homeostasis of animals in their natural habitats. C 2014 American Physiological Society.
Physiological mechanisms of silver toxicity (as silver nitrate) to the sensitive rainbow trout (O... more Physiological mechanisms of silver toxicity (as silver nitrate) to the sensitive rainbow trout (Oncorhynchus mykiss) (96 h LC50: 10.2 μg silver l−1, in soft, low chloride water) and the more tolerant European eel (Anguilla anguilla)(96 h LC50: 34.4 μg silver l−1, in the same water) were investigated during acute exposure to silver, using concentrations varying from 3 to 22 μg
Adult rainbow trout were pre-exposed to a sublethal concentration of waterborne cadmium (Cd, 26.7... more Adult rainbow trout were pre-exposed to a sublethal concentration of waterborne cadmium (Cd, 26.7 nmol/l) or waterborne zinc (Zn, 2294 nmol/l) for 30 days to induce acclimation. A single dose of radiolabeled Cd (64.4 nmol/kg) or Zn (183.8 nmol/kg) was injected into the vascular system of non-acclimated and Cd- or Zn-acclimated trout through indwelling arterial catheters. Subsequently, repetitive blood samples over 10 h and terminal tissue samples (liver, heart, bile, stomach, intestine, kidney, gills, muscle, and spleen) were taken to characterize the effect of metal acclimation on clearance kinetics in vivo. Plasma clearance of Cd in Cd-acclimated fish (0.726±0.015 and 0.477±0.012 ml/min per kg for total and newly accumulated Cd, respectively), was faster than that in non-acclimated trout (0.493±0.013 and 0.394±0.009 ml/min per kg). Unlike plasma Cd, the levels of Cd in red blood cells (RBCs) were 1.2–2.2 times higher in Cd-acclimated fish than in non-acclimated fish. At 10 h post-...
However, thermal change can alter lobster acid-base status over a time course of minutes. Acute i... more However, thermal change can alter lobster acid-base status over a time course of minutes. Acute increases in temperature trigger a respiratory compensated metabolic acidosis of the hemolymph. Both the strength and frequency of the lobster heartbeat in vitro are modulated by changes in pH within the physiological range measured in vivo. These observations suggest that changes in acid-base status triggered by thermal variations in the environment might modulate lobster cardiac performance in vivo.
It is well established that serotonin (5-HT; 5-hydroxytryptamine) plays a role in mammalian regul... more It is well established that serotonin (5-HT; 5-hydroxytryptamine) plays a role in mammalian regulation of the hypothalamic-pituitary-adrenal (HPA) axis via the 5-HT receptor subtype 1A (5-HT 1A ). To date, there has not been a comprehensive investigation of the molecular, pharmacological and physiological aspects of the 5-HT 1A receptor and its role in the activation of the hypothalamic-pituitary-interrenal (HPI) axis in teleost fish. The 5-HT 1A receptor of the Gulf toadfish (Opsanus beta) was cloned and sequenced, showing 67.5% amino acid similarity to the human homologue. The 5-HT 1A receptor was distributed throughout the brain, with the whole brain containing significantly higher levels of 5-HT 1A mRNA compared to all other tissues and the midbrain/diencephalon region containing significantly higher levels of transcript than any other brain region. Substantial levels of transcript were also found in the pituitary, while very low levels were in the kidney that contains the interrenal cells. Xenopus oocytes injected with toadfish 5-HT 1A receptor cRNA displayed significantly higher binding of [ 3 H]5-HT that was abolished by the mammalian 5-HT 1A receptor agonist, 8-OH-DPAT, indicating a conserved binding site of the toadfish 5-HT 1A receptor and a high specificity for the agonist. Supporting this, binding of [ 3 H]5-HT was not affected by the mammalian 5-HT 1B receptor agonist, 5-nonyloxytryptamine, the 5-HT 7 receptor antagonist, SB269970, or the 5-HT 2 receptor agonist, a-methylserotonin. Confirming these molecular and pharmacological findings, intravenous injection of 8-OH-DPAT stimulated the HPI axis to cause a 2-fold increase in circulating levels of cortisol. The present study of the 5-HT 1A receptor in a single teleost species illustrates the high conservation of this 5-HT receptor amongst vertebrates.
Adult crayfish (Cambarus diogenes diogenes) exposed to 8.41 Ϯ 0.17 g silver/L (19.4% as Ag ϩ ) in... more Adult crayfish (Cambarus diogenes diogenes) exposed to 8.41 Ϯ 0.17 g silver/L (19.4% as Ag ϩ ) in moderately hard freshwater under flow-through conditions for 96 h exhibited ionoregulatory disturbance, elevated metabolic ammonia (T amm ) production and substantial silver accumulation in the gills, hemolymph, and hepatopancreas. The ionoregulatory disturbance included both a generally reduced unidirectional Na ϩ influx and an increased unidirectional Na ϩ efflux, leading to a substantial net loss of Na ϩ from the silver-exposed crayfish. The Na ϩ uptake in silver-exposed crayfish differed overall from controls, while the increased Na ϩ efflux recovered to control values 48 h into the 96 h of exposure. The general inhibition of Na ϩ uptake could be explained by a reduced sodium/potassium-adenosine triphosphatase (Na/K-ATPase) activity in terminally obtained gill samples from the silverexposed crayfish. The silver-induced effect on Na ϩ uptake and loss translated to reduced hemolymph Na ϩ concentrations but not significantly reduced hemolymph Cl Ϫ concentrations. Hemolymph T amm and T amm efflux both increased in silver-exposed crayfish, indicating an increased metabolic T amm production. The present study demonstrates that the toxic mechanism of waterborne silver exposure in freshwater crayfish resembles that of freshwater teleost fish. The crayfish might therefore be a useful model system for extending current environmental regulatory strategies, currently based on teleost fish, to invertebrates.
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