COMPOUND D609 INHIBITS PHORBOL ESTER-STIMULATED PHOSPHOLIPASE-D ACTIVITY AND PHOSPHOLIPASE C-MEDIATED PHOSPHATIDYLETHANOLAMINE HYDROLYSIS

Tricyclodecan-9-yl-xanthogenate (compound D609) has recently been used in various cellular systems to specifically inhibit the activity of p hosphatidylcholine (PtdCho)-directed phospholipase C (PLC). Here we sh ow that in intact NIH 3T3 fibroblasts, concentrations of D609 (35 to 5 0 mu g/ml) which have been used to inhibit PLC activity also significa ntly inhibit phorbol ester-induced phospholipase D-mediated hydrolysis of both PtdCho and phosphatidylethanolamine (PtdEtn). In addition, in isolated membranes compound D609 also inhibited PLC-mediated PtdEtn h ydrolysis. The results indicate that compound D609 cannot be considere d as a specific inhibitor of PtdCho-directed PLC activity.