Active ion (NaCl) transport across isolated frog skin is discussed in relation to sodium and potassium composition and to O3 consumption of skin. A distinction is made between processes in skin related to "unidirectional active ion transport" and processes related to "maintenance electrolyte equilibrium;" i.e., ionic composition of skin. Several metabolic inhibitors were found that could be used in separating maintenance electrolyte equilibrium from unidirectional active ion transport. Fluoroacetate (up to 1 X 10-M/liter) did not affect maintenance electrolyte equilibrium, but severely diminished the rate of active ion transport. This could also be accomplished with azide and diethyl malonate when 1 X 10 -3 molar concentrations were used. When applied in higher concentrations, these two inhibitors, and several others, diminished active ion transport, but this was associated with changes in maintenance electrolyte equilibrium (gain of Na + by and loss of K + from skin). Similar observations were made when skins were subjected to K+-deficient media. Mersalyl and theophylline, in low concentrations, stimulated active ion transport without leading to changes in maintenance electrolyte equilibrium. Inhibition of'active ion transport was found accompanied by decrease, increase, and unaltered over-all 03 consumption, depending on the kind of chemical agent used. A provisional scheme of the mechanism of unidirectional active ion transport is proposed. It is conceived as a process of metabolically supported ion exchange adsorption, involving a carrier, forming complexes with K + and Na +, a trigger, K + ions, and two spatially separated metabolic pathways.

A study is presented on the effect of temperature on unidirectional active ion transport, resting electrolyte equilibrium (electrolyte composition), and oxygen consumption in isolated frog skin. The aims were twofold: first, to find out whether the rate of active transport can be changed without affecting the Na + and K + balance of skin itself; second, to arrive at minlmal ANa/AO2 values by correlating quantitatively inhibition of active ion transport with inhibition of O2 consumption. NaC1 transport was maximal at 20°C. At 28 ° and at temperatures below 20 °, rate of NaCI transport was diminished. In many instances NaCI transport was diminished in skinq which maintained their normal Na + and K + content. In several cases, however, neither rate of transport nor resting electrolyte equilibrium was affected; in other cases, both were.O2 consumption decreased when lowering the temperature over the range from 28 to 10°C. From a plot of log Qo2 against 1/T an activation energy of # = 13,700cal. was calculated, valid for the range from 10 to 20°C. It appeared that # was smaller for temperatures above 20°C. Working between l0 and 20 °, it was found that, on the average, 4 to 5 equivalents of Na + were transported for one m01e of O2 consumed in skins with undisturbed resting electrolyte equilibrium.