Differential effects of ouabain on host- and sindbis virus-specified protein synthesis.

Ouabain, a specific inhibitor of the membrane-associated Na⁺/K⁺-ATPase (sodium pump), has a differential effect on protein synthesis in Sindbis virus-infected and uninfected chick embryo fibroblast (CEF) cultures. At low concentrations, cell-specified protein synthesis is inhibited while Sindbis virus-directed protein synthesis is stimulated. At higher ouabain concentrations, which inhibit protein synthesis in uninfected CEF cells 95% or more, viral protein synthesis continues. Ouabain treatment of uninfected CEF cells raises the intracellular Na⁺ concentration and lowers the intracellular K⁺ concentration. The effect of Sindbis virus infection is similar. The changes in intracellular Na⁺ and K⁺ concentrations appear responsible for the selective inhibition of the translation of host cell mRNAs in Sindbis virus-infected or ouabain-treated CEF.