Xenopus laevis oocytes were injected with mRNA extracted from growth factor-responsive CCL39, Chinese hamster lung fibroblasts. The expression of functional growth factor receptors on the oocytes was demonstrated by growth factor-induced 45Ca2+ efflux. To determine the isozyme(s) of phospholipase C (PLC) coupled to growth factor receptors, growth factor-induced 45Ca2+ efflux were measured following coinjection of mRNA from CCL39 cells with PLC antibodies. PLC-γ1 antibody did not lead to loss of 45Ca2+ efflux induced by thrombin but resulted in loss of that induced by platelet-derived growth factor (PDGF). In contrast, PLC-δ1 antibody did not block PDGF-induced 45Ca2+ efflux but led to inhibition of thrombin-induced 45Ca2+ efflux. PLC-β1 antibody did not affect Ca2+ efflux by the treatment of either thrombin or PDGF. These results suggest that these growth factor receptors are coupled to specific effectors, i.e. thrombin receptor to PLC-δ1 and PDGF receptor to PLC-γ1.
