title: Regulation of passive potassium transport of normal and transformed 3T3 mouse cell cultures by external calcium concentration and temperature.
abstract: Regulation of passive potassium ion transport by the external calcium concentration and temperature was studied on cell cultures of 3T3 mouse cells and their DNA-virus transformed derivatives. Upon lowering of external calcium concentration, passive potassium efflux generally exhibits a sharp increase at about 0.1 mM. The fraction of calcium-regulated potassium efflux is largely independent of temperature in the cases of the transformed cells, but shows a sharp increase for 3T3 cells upon increasing temperature above 32 degrees C. In the same range of temperature, the 3T3 cells exhibit the phenomenon of high-temperature inactivation of the residual potassium efflux at 1 mM external calcium. At comparable cellular growth densities, the transformed cell lines do not show high-temperature inactivation of "residual" potassium efflux. These results are consistent with the notion of a decisive role of the internal K+ concentration in the cell-density dependent regulation of cell proliferation. In particular, the growth-inhibiting effect of lowering the external Ca2+ concentrations is considered as largely due to a rise of passive K+ efflux and a subsequent decrease of internal K+ concentration. The experimental data on the Ca2+ dependence of passive K+ flux are quantitatively described by a theoretical model based on the constant field relations including negative surface charges on the external face of the membrane, which cooperatively bind Ca2+ ions and may concomitantly undergo a lateral redistribution. The present evidence is consistent with acidic phospholipids as representing these negative surface charges.
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology*; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D051379:Mice; D008954:Models, Biological; D011120:Polyomavirus; D011188:Potassium / Q000378:metabolism*; D013539:Simian virus 40; D013696:Temperature; D013816:Thermodynamics
chemical_list: D011188:Potassium; D002118:Calcium