Compensation of progressive hypercapnia in the toad (Bufo marinus) and the bullfrog (Rana catesbeiana).
Toads (Bufo marinus L.) and bullfrogs (Rana catesbeiana Shaw) were subjected to a series of 24 h step increases in aerial CO2 (2, 4, 6 and 8%) to assess the degree of extracellular pH compensation at each CO2 level and to ascertain the importance of cutaneous ion transport in this process. Elevation of plasma [HCO3-] occurs during the 24 h period, with the bullfrogs showing a greater ability to compensate at each step. There was no indication that a [HCO3-] threshold of 30 mmol l-1 existed in either species, although bullfrogs appeared to have a greater compensatory potential when exposed to the higher levels of CO2. The results of the ion flux experiments suggest that neither the terrestrial Bufo nor the semi-aquatic Rana use their skin to any great extent for acid-base balance during hypercapnia.
Toews
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Biological Sciences Department, California State Polytechnic University, Pomona 91768.
Stiffler
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D000136:Acid-Base Equilibrium; D000222:Adaptation, Physiological; D000818:Animals; D002024:Bufo marinus / Q000502:physiology*; D002245:Carbon Dioxide; D004781:Environmental Exposure; D006935:Hypercapnia; D011892:Rana catesbeiana / Q000502:physiology*
D002245:Carbon Dioxide