PLATELET-DERIVED GROWTH-FACTOR BLOCKS THE INCREASE IN INTRACELLULAR FREE CA2+ CAUSED BY CALCIUM IONOPHORES AND A VOLATILE ANESTHETIC AGENT IN SWISS 3T3 FIBROBLASTS WITHOUT ALTERING TOXICITY

Platelet-derived growth factor (PDGF) produced an almost complete block of the increase in intracellular free Ca2+ concentration ([Ca2+]i) in Swiss 3T3 fibroblasts caused by the Ca2+ -selective ionophores 4-bromo-A23187 and ionomycin, and by the volatile anesthetic agent halothane. The effect of PDGF was similar to the decreased [Ca2+]i response to Ca2+ -ionophores produced by phorbol 12-myristate 13-acetate, an activator of protein kinase C. There was no effect of PDGF or PMA on the acute or delayed toxicity of the Ca2+ -ionophores to Swiss 3T3 cells, suggesting tha the increase in [Ca2+]i is not the direct cause of toxicity of these agents.