POLYUNSATURATED FATTY-ACIDS DO NOT ACTIVATE PROTEIN-KINASE-C IN THE TESTIS OF THE GOLDFISH (CARASSIUS-AURATUS)

Earlier studies have established that polyunsaturated fatty acids (PUF A) such as eicosapentaenoic acid and docosahexaenoic acid inhibit ster oid production in the goldfish testis. As PUFA inhibit testicular ster oidogenesis in the rat through activation of protein kinase C (PKC), t he present studies were undertaken to characterize the properties of P KC in the goldfish testis and to test the effects of selected PUFA on PKC activity. PKC activity was quantified in goldfish testis homogenat e following partial purification by DEAE-cellulose chromatography by d etermining the transfer of radiolabelled phosphate from [gamma - P-32] ATP to histone III-S. Testicular PKC activity was defined by the amoun t of protein phosphorylation in the presence of phosphatidylserine, ph osphatidylcholine, Ca2+ ions and diolein (a 1,2-diacylglycerol analog) above that obtained in response to Ca2+ ions alone. Western blot anal ysis of a crude testis homogenate using an antibody specific to the al pha and beta isoforms of mammalian PKC led to the identification a sin gle band of protein (80 kD) that co-migrated with PKC from rabbit brai n cytosol. Addition of arachidonic, eicosapentaenoic or docosahexaenoi c acids failed to activate PKC. However, PKC activity stimulated by ph ospholipid, Ca2+ ions and diolein was inhibited in a dose related fash ion by all of these fatty acids. These studies suggest that the inhibi tory effects of EPA and DHA on testicular steroidogenesis are not medi ated by activation of PKC. The lack of effect of PUFA on PKC activity in the goldfish testis suggests that either the distribution of PKC is oforms differs between the testis of mammals and fish or that PKC is n ot activated by PUFA in the goldfish.