Calcium permeability of Ehrlich ascites tumour cell plasma membrane in vivo

Abstract Passive Ca 2+ entry into Ehrlich ascites tumour cells has been investigated. Passive equilibration of Ca 2+ takes place in ascites tumour cells only under conditions of exhaustive energy depletion. The specific Ca 2+ ionophore A23187 does not affect Ca 2+ entry into ascites tumour cells under active metabolic conditions, but it increases the rate of Ca 2+ equilibration in ascites tumour cells in the early stages of energy depletion. The results of the present experiments lead to the conclusion that in ascites tumour cell plasma membrane Ca 2+ permeability is not a limiting step in the regulation of intracellular calcium content, while the energy-dependent Ca 2+ extrusion is the main mechanism that prevents uncontrolled intracellular Ca 2+ increase. The results taken together support the hypothesis that increased Ca 2+ influx into the cell, caused by plasma membrane alteration, is responsible for permanently elevated mitotic activity and for deranged metabolic behaviour of these neoplastic cells.