Benzene and toluene activate protein kinase C.

Protein kinase C plays a pivotal role in the transduction of signals controlling cell activation. A number of tumor promoters including phorbol esters activate the enzyme by substituting for diacylglycerol, the intracellular messenger of physiological ligands. In contrast, chloroform-induced protein kinase C activation does not appear to be mediated through the same mechanism. In vitro studies and experiments on intact platelets have revealed that benzene and toluene are also activators of protein kinase C. The data suggest that these drugs, which do not inhibit [3H]12-O-tetradecanoylphorbol-13-acetate binding to the enzyme, probably act in a chloroform-like manner.