ROLE OF SPECIFIC ISOFORMS OF PROTEIN-KINASE-C IN ANGIOTENSIN-II AND LIPOXYGENASE ACTION IN RAT ADRENAL GLOMERULOSA CELLS

Evidence indicates that the lipoxygenase (LO) pathway of arachidonic a cid is a key mediator of angiotensin II (AII)-induced aldosterone synt hesis in adrenal glomerulosa cells. Although protein kinase C (PKC) ma y play a role in AII action, the precise PKC isoforms involved and LO products can activate PKC is not clear. We therefore evaluated the eff ect of AII and LO products such as 12- and 15-hydroxyeicosatetraenoic acids (HETEs) on PKC activation in isolated rat adrenal glomerulosa ce lls. PKC activity was measured by the phosphorylation of a PKC specifi c peptide while the PKC isoforms were identified by Western immunoblot ting using antibodies that recognize the alpha, beta, gamma or epsilon isoforms of PKC. Treatment of the cells for 15 min with AII (10(-8)M) or the LO products 12- or 15-HETE caused a marked increase in PKC act ivity in membrane fractions with reciprocal decreases in the cytosolic PKC activity. Rat glomerulosa cells expressed only the alpha, and eps ilon isoforms of PKC. AII increased membrane bound levels of both PKC- alpha and epsilon (1.9- and 1.5-fold, respectively), whereas the LO pr oducts predominantly activated PKC-epsilon. Reciprocal decreases in im munoreactive cytosolic PKC levels were seen. AII-induced aldosterone s ynthesis was blocked by H-7 and retinal as well as by a PKC-specific p seudosubstrate inhibitor, PKC(19-36). These results suggest that AII a nd LO pathway-induced actions in the adrenal glomerulosa. may be media ted by specific PKC isoforms.