Compound D609 inhibits phorbol ester-stimulated phospholipase D activity and phospholipase C-mediated...

Tricyclodecan-9-yl-xanthogenate (compound D609) has recently been used in various cellular systems to specifically inhibit the activity of phosphatidylcholine (PtdCho)-directed phospholipase C (PLC). Here we show that in intact NIH 3T3 fibroblasts, concentrations of D609 (35 to 50 micrograms/ml) which have been used to inhibit PLC activity also significantly 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 hydrolysis. The results indicate that compound D609 cannot be considered as a specific inhibitor of PtdCho-directed PLC activity.