Lack of an effect of novel inhibitors with high specificity for protein kinase C on the action of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate on mouse skin in vivo.

The inhibitory effects of three novel staurosporine-derived compounds were tested with five different types of protein kinases, including protein kinase C (PKC). IC50 values of two of these compounds were found to be 300 to > 5000 times lower for PKC alpha beta gamma (a mixture of the PKC isoenzymes alpha, beta and gamma) than for any of the other protein kinases. The inhibitory action of the most selective inhibitor was tested also with the Ca(2+)-unresponsive PKC isoenzyme delta and was found to suppress PKC alpha beta gamma and PKC delta differentially. The highly specific PKC inhibitors are active both in cell culture and in vivo. They inhibit the PKC-catalyzed phosphorylation of the specific PKC substrate MARCKS in Swiss-3T3 fibroblasts and the okadaic acid-induced edema of the mouse ear. However, the more complex biological processes triggered by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate in mouse skin, such as inflammation, stimulation of cellular hyperproliferation and tumor promotion, remain largely unaffected upon topical application of these compounds.