Effect of Amiloride on sodium transport in frog skin

Summary The effect of Amiloride on several parameters of sodium transport was investigated on the isolated frog skin. Amiloride at a concentration of 10^–4 M/l decreased the sodium concentration in the sodium transport pool from 8.9 meq/kg cell water to 3.7 meq/kg cell water. No effect was observed on the intracellular sodium which is exchangeable from the corium side. Short circuit current and unidirectional sodium influx were diminished to the same extent whilst the unidirectional sodium efflux was not affected. In contrast to the short circuit current, which reaches a new steady state value within seconds, the unidirectional sodium influx reaches its new steady state with a half-time of 3.3 min. From the difference in the time courses of the decreases of short circuit current and unidirectional sodium influx, an amount of sodium could be calculated which agreed well with the directly measured fall in the sodium transport pool.The results provide further evidence for the concept that Amiloride inhibits the passive entrance of sodium into the sodium transport compartment, without influencing the transport capacity of the sodium pump.Supported by the Deutsche Forschungsgemeinschaft.