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Titolo:
Ion and acid-base regulation in the freshwater mummichog (Fundulus heteroclitus): a departure from the standard model for freshwater teleosts
Autore:
Patrick, ML; Wood, CM;
Indirizzi:
McMaster Univ, Dept Biol, Hamilton, ON L8S 4K1, Canada McMaster Univ Hamilton ON Canada L8S 4K1 ol, Hamilton, ON L8S 4K1, Canada
Titolo Testata:
COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR AND INTEGRATIVE PHYSIOLOGY
fascicolo: 4, volume: 122, anno: 1999,
pagine: 445 - 456
SICI:
1095-6433(199904)122:4<445:IAARIT>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
WATER RAINBOW-TROUT; EEL ANGUILLA-ROSTRATA; CL UPTAKE KINETICS; SALMO-GAIRDNERI; ENVIRONMENTAL HYPEROXIA; PROTON PUMP; ALKALINE ENVIRONMENT; ONCORHYNCHUS-MYKISS; DIFFUSIVE EFFLUXES; EQUIVALENT FLUXES;
Keywords:
acid-base balance; freshwater ion regulation; Fundulus heteroclitus; mummichog; killifish; teleost; ammonia excretion; urea excretion;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Life Sciences
Citazioni:
41
Recensione:
Indirizzi per estratti:
Indirizzo: Patrick, ML Univ Calif Irvine, Dept Ecol & Evolutionary Biol, Irvine, CA 92697 USA Univ Calif Irvine Irvine CA USA 92697 l, Irvine, CA 92697 USA
Citazione:
M.L. Patrick e C.M. Wood, "Ion and acid-base regulation in the freshwater mummichog (Fundulus heteroclitus): a departure from the standard model for freshwater teleosts", COMP BIOC A, 122(4), 1999, pp. 445-456

Abstract

Ion and acid-base balance were examined in the freshwater-adapted mummichog (Fundulus heteroclitus) using a series of treatments designed to perturb the coupling mechanisms. Unidirectional Cl- uptake (J(in)(Cl)) was extremely low whereas J(in)(Na) was substantial (three- to sixfold higher); comparable differences occurred in unidirectional efflux rates (J(out)(Cl), J(out)(Na)). J(in)(Cl) was refractory to all treatments, suggesting that Cl-/baseexchange was unimportant or absent. Indeed, no base excretion or modulation of ion fluxes occurred for acid-base balance for up to 8 h after NaHCO3- loading (injections of 1000 or 3000 nequiv.g(-1)). Acute environmental low pH (4.5) and amiloride (10(-4) M) treatments caused concurrent inhibition of J(in)(Na) and net H+ excretion (J(net)(H+)) , indicating the presence of Na+/H+ exchange. J(in)(Na) was elevated and J(net)(H+) restored during recovery from both treatments, but this exchange did not appear to be dynamically adjusted for acid-base homeostasis. High external ammonia exposure (` mmol . l(-1)) initially blocked ammonia excretion (J(net)(Amm)) but had no effect on J(in)(Na), whereas high pH (9.4) reduced both J(net)(Amm) and J(in)(Na). Inhibition of J(in)(Na) by the low pH and amiloride treatments had noeffect on J(net)(Amm). These results indicate that ammonia excretion is entirely diffusive and independent of both Na+ uptake and the protons that are transported via the Na+/H+ coupling. In addition, ureagenesis served as acompensatory mechanism during high external ammonia exposure, as a marked elevation in urea excretion partially replaced the inhibited J(net)(Amm). In all treatments, changes in the Na+-Cl- net flux differential were consistent with changes in J(net)(H+) measured by traditional water titration techniques, indicating that the former can be used as an estimate of the acid-base status of the fish. Overall, the results demonstrate that the freshwater-adapted F. heteroclitus does not conform to the ion/acid-base relationships described in the standard model based on commonly studied species such as trout, goldfish, and catfish. (C) 1999 Elsevier Science Inc. All rights reserved.

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Documento generato il 01/12/20 alle ore 22:42:00