Effects of amiloride on active sodium transport by the isolated frog skin: evidence concerning site of action

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Abstract
1 Amiloride reduces short-circuit current and potential difference across the isolated frog skin. 2 Isotopically measured sodium influx and efflux are diminished. 3 Total electrical conductance and partial sodium conductance are diminished, the reduction in total conductance being entirely accounted for by the reduction in partial sodium conductance. 4 The effect of antidiuretic hormone (ADH), cyclic 3′5′-adenosine monophosphate (cyclic AMP) and theophylline can be antagonized by pretreatment with amiloride but the antagonism can be abolished by increasing the concentration of these compounds. 5 Amiloride has no effect on oxygen consumption in concentrations which inhibit sodium transport. However, it prevents the stimulatory effect of ADH on oxygen consumption. 6 The results are consistent with an action of amiloride at the passive outside membrane of the transporting cells of isolated frog skin.