Alterations in monovalent cation transport in sindbis virus-infected chick cells

Abstract

Influx experiments using the potassium tracer 86Rb + indicated that the activity of the Na +K + ATPase, or sodium pump, was reduced 40–50% as a consequence of Sindbis virus infection of avian fibroblasts. The inhibition of this ouabain-sensitive, active transport system temporally correlated with a decrease in the intracellular K + concentration and the termination of cellular protein synthesis. By contrast, the rate of influx facilitated by the furosemide-sensitive (Na +K +Cl −) cotransport system was only slightly depressed. Efflux experiments indicated that no alterations in the relative rate of nonspecific permeability or “leakage” of K + could be detected in chick cells infected by Sindbis virus. The amount of [ 3H]ouabain bound to Sindbis virus-infected cells paralleled the reduction in Na +K + ATPase activity. These binding studies revealed no difference in the number of Na + pump sites. The K m of ouabain binding, however, increased approximately 3.5-fold in the virus-infected cells. No change in the apparent affinity of the Na + pump for K +could be detected, yet the V max for ouabain-sensitive K + transport was decreased. These experiments suggest that a reduction in Na +K + ATPase turnover results in the altered intracellular monovalent cation levels found in Sindbis virus-infected chick cells.