Activation of protein kinase C by an aromatic xenobiotic diacylglycerol analogue.

A number of xenobiotic carboxylic acids, including 3-phenoxybenzoic acid (3PBA), have been shown to form 'hybrid' di- and tri-acylglycerols both in vivo and in vitro. Experiments were carried out to test the hypothesis that naturally occurring xenobiotic diacylglycerols may stimulate protein kinase C. The activity of protein kinase C was measured in the presence of different diacylglycerols. 1-Acyl-2-(3PBA)-sn-glycerol but not 1,2-di-3PBA-sn-glycerol stimulated protein kinase C, but less effectively than either dioleoylglycerol or phorbol 12-myristate 13-acetate. The xenobiotic diacylglycerols were also more resistant to lipolysis. The possibility exists therefore that some xenobiotic diacylglycerols may behave, like phorbol diesters, as tumour promoters.