Abstract

Washed erythrocyte ghosts, labeled with Na²³, were used to study the effects of purine nucleosides on active transport of Na⁺. Activation of the Na⁺ pump by inosine and adenosine was demonstrated at nucleoside concentrations much lower than those used by other investigators. Several other purine nucleosides were also shown to have similar effects. No correlation was found between the effects of various nucleosides on the Na⁺ pump and their ability to act as substrates for nucleoside phosphorylase. Activation of the Na⁺ pump by inosine in the absence of utilization of ribose moiety of inosine was demonstrated. Although the mechanisms of these actions of nucleosides are not clear, it was shown that the activation of the Na⁺ pump occurred when unknown endogenous substracts of ghosts were converted to lactate. The demonstration of the presence of these substrates suggests that, when the relation of ghost metabolism to ion transport mechanisms is studied, the fate of the endogenous substrates must be considered.