Chloride dependence of active sodium transport in frog skin: the role of intercellular spaces.

Abstract

The replacement of Cl by a non-penetrating anion in solution bathing either the outside or both sides of frog skin [Bufo bufo; Rana temporaria] causes a fall in the short-circuit current. When Cl is replaced by a non-penetrating anion in the solution bathing the outside of the frog skin the Isc [intercellular spaces] was still a correct measure of the net Na transport. Under the same conditions both active and shunt paths were affected. There was a decrease in Isc, Na influx, amiloride-dependent conductance and initial Na uptake across the external barrier, together with a decrease in Cl-backfluxes and amiloride-independent conductance. There also is a decrease in water permeability and a reduction in size of the intercellular spaces. The removal of Cl did not appear to affect the entry step of Na but may have an effect on the shunt path. This in turn may change the active Na transport.