Dependence of sodium and chloride transports on chloride concentration in isolated frog skin

Abstract

The influence of the ambient chloride concentration on the sodium and chloride transports was determined in isolated frog skin. When the ambient chloride concentration was raised, the net chloride flux increased abruptly, stabilized at low chloride concentrations (5-10 m[image]), and showed another increase starting near 70 m[image] chloride. The chloride efflux was linear with the chloride concentration, and the permeability for chloride was 3.3 x 10-6 cm/sec. The sodium net flux decreased by 67% from 0 to 20 m[image] chloride, and then increased up to 118 m[image] chloride. The ratio of sodium net flux over chloride net flux decreased linearly with increasing chloride concentration. An ATPase enzyme showed a 15% decrease of its activity at 20 mM chloride. 36ci and 22Na washouts toward the outside of the skin did not respond to changes in the chloride concentration. It is concluded that the chloride transport does not follow simple Michaelis-Menten kinetic, and that an interdependence between the sodium and chloride transports exists, which can be described by a coupling superimposed on a competition between them.