Mitogen‐induced oscillations of membrane potential and Ca2+ in human fibroblasts

Abstract
Using the whole‐cell technique, we have measured recurring hyperpolarizations induced by fetal calf serum and bradykinin in human fibroblasts. By coupling fura‐2 microfluorimetry to electrophysiology, we have also measured directly cytosolic Ca2+ and found that Ca2+ oscillations occur in synchrony with membrane currents. Mitogen stimulation of cells in which intracellular K+ had been replaced with Cs+ resulted in the abolishment of the outward current. We conclude then that the mitogen‐induced recurring hyperpolarizations in human fibroblasts are due to the opening of Ca2+‐activated K+ channels.