The Role of Physico-Chemical Buffering and of Bicarbonate Transfer Processes in Intracellular pH Regulation in Response to Changes of Temperature in the Larger Spotted Dogfish (Scyliorhinus Stellaris)

Abstract

In order to evaluate the contributions of physico-chemical buffering to the adjustment of intracellular pH in response to changes of temperature in tissues of dogfish (Scyliorhinus stellaris), the CO₂ equilibration method for the determination of intracellular buffer values was modified to yield data for the mathematical simulation of the intracellular compartments as closed buffer systems, and for the calculation of transmembrane bicarbonate transfer in vivo. The respective buffer values of imidazole-like and phosphate-like buffer substances were estimated to be about 39 and 11 in white muscle, 21 and 18 in red muscle and 27 and 10 mequiv/(pH.1 cell water) in heart muscle. In white muscle, the observed changes of intracellular pH can be explained by physico-chemical buffering and changes of P_CO2. In red muscle and heart muscle considerable amounts of bicarbonate have additionally to be transferred across the cell membrane to achieve the temperature-dependent variations of pH observed in vivo.