Acidification and sodium entry in frog skin epithelium.

ABSTRACT

Acidification of the external medium by isolated frog skin epithelium (Rana catesbeiana, Rana temporaria, and Caudiververa caudiververa) and its relationship to Na+ uptake was studied. Acidification was measured by the pH-stat technique under short-circuit or open-circuit conditions. The results of this study demonstrate that (a) acidification by these species of in vitro frog skins is not directly coupled to Na+ or anion transport; (b) acidification can be inhibited by the diuretic drug amiloride, but only at high external Na+ concentrations; (c) acidification rate in these species of frog skin is controlled in part by the metabolic production of CO2; and (d) the positive correlation between net Na+ absorption and net acidification observed in whole animal studies could not be replicated in the in vitro skin preparation, even when the frogs were first chronically stressed by salt depletion, a physiological state comparable to that used in the in vivo experiments.