Regulation of passive membrane permeability for potassium ions by cell density of 3T3 and SV40-3T3 cells.

The passive K⁺ permeability of 3T3 and SV40-3T3 cells was evaluated from experiments on passive K⁺ efflux and electrical transmembrane potential measurements at different cell growth densities, external calcium concentrations and temperatures. Passive K⁺ permeability was shown to decrease markedly with increasing cell growth density, to increase with the lowering of external calcium concentration, and at low cell densities to be higher at low temperature (25 °C) than at physiological temperature (37 °C). These and further results taken from the literature are fully consistent with the notion of regulation of proliferation being effected by control of intracellular K⁺ concentrations. The phenomenon of high temperature inactivation of passive K⁺ permeabilities observed at low cell densities is discussed in analogy to recent results on model systems from phospholipid/cholesterol doted with channel-forming antibiotics.