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Title: | Limited extracellular but complete intracellular acid-base regulation during short-term environmental hypercapnia in the armoured catfish, Liposarcus pardalis |
Authors: | Brauner, Colin John Wang, Tobias Wang, Yuxiang Richards, Jeffrey G. Gonzalez, Richard J. Bernier, Nicholas J. Xi, W. Patrick, Marjorie L. Val, Adalberto Luis |
Keywords: | Carbon Dioxide Fresh Water Sodium Acid Base Balance Analysis Of Variance Animals Blood Catfish Comparative Study Heart Muscle Liver Metabolism Ph Physiology Acidosis, Respiratory Scintillation Counting Muscle, Skeletal Time Acid-base Equilibrium Acidosis, Respiratory Analysis Of Variance Animal Carbon Dioxide Catfishes Fresh Water Hydrogen-ion Concentration Liver Muscle, Skeletal Myocardium Scintillation Counting Sodium Radioisotopes Time Factors Callichthys Callichthys Catfish Liposarcus Liposarcus Pardalis Oligacanthorhynchus Pisces Teleost Fish Teleostei Vertebrata |
Issue Date: | 2004 |
metadata.dc.publisher.journal: | Journal of Experimental Biology |
metadata.dc.relation.ispartof: | Volume 207, Número 19, Pags. 3381-3390 |
Abstract: | Environmental hypercapnia induces a respiratory acidosis that is usually compensated within 24-96 h in freshwater fish. Water ionic composition has a large influence on both the rate and degree of pH recovery during hypercapnia. Waters of the Amazon are characteristically dilute in ions, which may have consequences for acid-base regulation during environmental hypercapnia in endemic fishes. The armoured catfish Liposarcus pardalis, from the Amazon, was exposed to a water PCO2 of 7, 14 or 42 mmHg in soft water (in μmol l-1: Na+, 15, Cl-, 16, K+, 9, Ca2+, 9, Mg2+, 2). Blood pH fell within 2 h from a normocapnic value of 7.90±0.03 to 7.56±0.04, 7.34±0.05 and 6.99±0.02, respectively. Only minor extracellular pH (pHe) recovery was observed in the subsequent 24-96 h. Despite the pronounced extracellular acidosis, intracellular pH (pHi) of the heart, liver and white muscle was tightly regulated within 6 h (the earliest time at which these parameters were measured) via a rapid accumulation of intracellular HCO3-. While most fish regulate pHi during exposure to environmental hypercapnia, the time course for this is usually similar to that for pHe regulation. The degree of extracellular acidosis tolerated by L. pardalis, and the ability to regulate pHi in the face of an extracellular acidosis, are the greatest reported to date in a teleost fish. The preferential regulation of pHi in the face of a largely uncompensated extracellular acidosis in L. pardalis is rare among vertebrates, and it is not known whether this is associated with the ability to air-breathe and tolerate aerial exposure, or living in water dilute in counter ions, or with other environmental or evolutionary selective pressures. The ubiquity of this strategy among Amazonian fishes and the mechanisms employed by L. pardalis are clearly worthy of further study. |
metadata.dc.identifier.doi: | 10.1242/jeb.01144 |
Appears in Collections: | Artigos |
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