1. The transport of sodium by frog skin and the maintenance of normal potassium levels within the cells of the skin are both dependent on metabolism and on a supply of phosphate bond energy. 2. Except for the common requirement of phosphate bond energy, the transfer mechanism for sodium and the mechanism for maintaining intracellular potassium appear to be independent. 3. The xanthines specifically inhibit the sodium transfer mechanism; at higher concentrations, they depress metabolism and cause loss of potassium from the skin.
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