Interactions Between Transcutaneous Ion Transfer Processes and Carbon Dioxide Excretion in Amphibians

Abstract

SYNOPSIS. The amphibian skin possesses a wide variety of physiological functions in that it constitutes not only the major organ for respiratory CO2 exchange but also plays important roles for ionic as well as osmotic balance. Apart from the simple transcutaneous diffusion of CO2 down its partial pressure gradient, acid-base relevant ion exchange mechanisms in the skin may also be important in overall pH regulation in these animals. The skin of some frogs, for example, contains mechanisms for the exchange of Na$/H$ and HCO3−/Cl− in which NaCl is actively transported into the animal in exchange for H$ and HCO3−. While such exchange mechanisms have often been studied in the context of osmoregulation in freshwater environments, their potential importance in acid-base regulation have been largely unexplored. The present paper reviews the evidence for participation of cutaneous ion transfer mechanisms in the overall regulation of CO2 excretion and acid-base balance in amphibians.