Vaccinia virus-induced changes in [Na+] and [K+] in HeLa cells

A flame photometric technique is described for determining average values for intracellular [Na+] and [K+] in HeLa cells. Ion measurements were made on unwashed cells disrupted ultrasonically in the presence of residual medium; corrections for the latter were made by measurement of extracellular volume in cell plus medium preparations using 125I-labelled polyvinylpyrrolidone (PVP) as the marker in an isotopic dilution technique. Accurate measurement of the volume occupied by the cells was critical and required a concentration step. This was achieved by concentrating cell suspensions in a microhaematocrit centrifuge using calibrated capillary tubes. Most reliable values were obtained in our system using HeLa S3 (suspension) cells grown as monolayers, which were removed by EDTA and held in suspension for a minimum of 2 h. Uninfected HeLa cells had values of 20 to 30 and 110 to 120 mM for Na+ and K+ respectively. At 13 h after inoculation with vaccinia virus, a dramatic reversal in [Na+] and [K+] occurred, but throughout the infection cycle the total [Na+ + K+] varied little. The significance of these data is discussed in relation to theories of virus-induced modulation of protein synthesis in infected cells and in cell-free systems.