Sodium and rubidium uptake in cells transformed by Rous sarcoma virus

Abstract

Rates of uptake and intracellular concentrations of monovalent cations were measured in virus‐transformed and nontransformed chick embryo (CE) cells. Uptake of ²²Na⁺ into cells transformed by the BH strain of Rous sarcoma virus (RSV‐BH) (CE‐BH) was about double the rate of uptake into CE cells, or cells transformed by the Schmidt‐Ruppin strain (RSV‐SR): CE‐SR. Likewise, the rate of efflux of ²²Na⁺ was greater in CE‐BH cells than in CE or CE‐SR cells. The greater permeability of CE‐BH cells to Na⁺ was apparent in higher intracellular Na⁺ concentrations. Experiments with cells exhibiting temperature‐dependent transformation showed that new RNA and protein synthesis was a requirement for the acquisition of increased Na⁺ permeability, suggesting that the change is an indirect effect of the virus‐coded transformation‐inducing protein. Rates of ⁸⁶Rb⁺ uptake, used as a measure of K⁺ influx, were indistinguishable in CE, CE‐BH, and CE‐SR cells. Also, equilibrium intracellular levels of ⁸⁶Rb⁺ were similar in transformed and nontransformed cells, as were observed concentrations of K⁺. Also, no differences in ATPase activity, as indicated by ouabain binding or temperature sensitivity, were observed. We conclude that monovalent cations play no direct role in RSV‐induced transformation, although the higher levels of Na⁺ in CE‐BH cells may be responsible for other distinguishing biochemical features of these cells.