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Blood Gases, and Extracellular/Intracellular Acid-Base Status as a Function of Temperature in the Anuran Amphibians Xenopus Laevis and Bufo Marinus
1 Abteilung Physiologie, Max-Planck-Institut für experimentelle Medizin, Göttingen, FRG; Department of Biology, Dalhousie University, Halifax, Nova Scotia, B3H4J1, Canada
2 Abteilung Physiologie, Max-Planck-Institut für experimentelle Medizin, Göttingen, FRG; Department of Zoophysiology, University of Aarhus, DK-8000 Aarhus, Denmark
3 Abteilung Physiologie, Max-Planck-Institut für experimentelle Medizin, Göttingen, FRG
Blood gases, and parameters of the extracellular and intracellular acid-base status, were measured in the anuran amphibians Bufo marinus and Xenopus laevis acclimated to temperatures of 10, 20 and 30°C for 12 days. Arterial POO2 rose with temperature so that approximately constant oxygen saturation of the blood was maintained, a phenomenon explained on the basis of models for O2 transport in animals with central vascular shunts and temperature-dependent shifts in O2 equilibrium characteristics. Arterial plasma pH of both species varied inversely with temperature, the pH/temperature coefficient being not significantly different from that required for constant relative alkalinity or dissociation of imidazole. The change in plasma pH was brought about mainly by changes in PCOCO2 although plasma bicarbonate concentration also changed significantly. Intracellular pH/temperature relationships were found to be non-linear in most of the tissues. There was considerable variability among body tissue compartments and between the two species. These data confirm that the various tissue compartments in ectotherms maintain unique 
pH/t relationships, and indicate that measurement of extracellular pH as a function of temperature is not a good indicator for alphastat-type, temperature-dependent, acid-base regulation.
Key words: acid-base regulation, Amphibia, blood gases, Bufo marinus, pH/t, imidazole alphastat, intracellular pH, Xenopus laevis
Accepted on March 4, 1987
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