Determination of the ENa of from skin from studies of its current-voltage relationship

Abstract

Studies were done to test the idea that the emf of the sodium pump (ENa) of isolated frog skin could be estimated directly from studies of its current-voltage relationship. ENa was estimated in two ways: a) from the bidirectional sodium flux ratio according to Ussing and Zerahn, and b) from the values of open-circuit voltage, short-circuit current, and the shunt resistance estimated when the [Na] of the outer solution was reduced to zero. When the values of ENa were compared with the values of E1 obtained from the current-voltage relationships, they were found to be the same despite considerable variability in the values of ENa between skins (77-168 mV). In general, the values of ENa were considerably higher when the skins were bathed with sulfate-Ringer as compared with chloride-Ringer solution. These data are compatible with the idea that in nonedge-damaged frog skin, the unidirectional sodium fluxes were confined primarily to active transport pathways alone, and, accordingly, they may be excluded from parallel-shunt pathways.