CAPACITATIVE CALCIUM-ENTRY IS INHIBITED IN VASCULAR ENDOTHELIAL-CELLSBY DISRUPTION OF CYTOSKELETAL MICROFILAMENTS

The role of an intact cytoskeleton for store-operated ('capacitative') Ca2+ influx was investigated in single cultured vascular endothelial cells. Capacitative Ca2+ entry was measured as changes of cytoplasmic Ca2+ concentration ([Ca2+](i)) induced by depletion of Ca2+ stores wit h thapsigargin. In cells pretreated with cytochalasin D, an agent that disrupts the microfilament network of the cytoskeleton, as confirmed with FITC-phalloidin staining, capacitative Ca2+ entry was inhibited, Cytochalasin D did not affect basal [Ca2+](i) nor ATP-induced increase s of [Ca2+](i), indicating that release of Ca2+ from intracellular sto res through the inositol-phosphate pathway was intact. These results s uggest that microfilaments are an integral part of the mechanism for c apacitative Ca2+ entry. The necessity for an intact cytoskeleton favor s a conformational coupling model for store-operated Ca2+ influx. (C) Federation of European Biochemical Societies.