CHARACTERIZATION OF PROTEIN-KINASE-C IN RAT AND HUMAN PROSTATES

The properties of protein kinase C (PKC) activity have been studied in cytosolic and membrane fractions from rat and human prostate. ion exchange chromatography indicated the existence of different PKC isoforms, PKC from rat ventral prostate behaved as a classical Ca2+ and phospholipid-dependent enzyme and was activated by 1,2-diacylglycerol as well as by high concentrations of arachidonic acid. PKC activity in the cytosolic fraction was higher and presented different cofactor requirements than that in the membrane fraction. PKC from human benign hyperplastic prostate was also phospholipid dependent, activated by tumor-promotong phorbol esters, and appeared to belong to the group of PKC isozymes which lack Ca2+ sensitivity. Human prostatic PKC activity appeared to be of similar nature in both membrane and cytosolic fractions but the specific activity was higher in the particulate preparation which could be related to the stage of endogenous activation of the enzyme. These results extend previous observations in rat ventral prostate and present evidences on the human counterpart. Forthcoming experiments are needed to establish the exact nature of PKC isozymes and their physiological and pathophysiological role in this gland.