The long-term goals of this project were: 1) to examine the nature of extracellular and intracellular signals controlling expression of tyrosine hydroxylase (TH), phenylethanolamine-N-methyl-transferase (PNMT), and proenkephalin (pEK) genes; 2) to determine whether these genes are differentially regulated; 3) to determine roles of transcription and post-transcriptional mechanisms in such regulations; and 4) to examine the possible role of nuclear oncogenes in coordinating the regulation of TH, PNMT, and pEK genes. Previous studies from our laboratory suggest that protein kinase C (PKC) is involved in the angiotensin II (AII) induced increase in the expression of genes encoding proenkephalin and catecholamine biosynthesizing enzymes in primary cultured bovine adrenal medullary (BAM) cells. The purpose of this study was to examine the effects of [Sar1]-AII (S1-AII), an AII agonist, on PKC activity in BAM cells. Short-term incubation with S1-AII produced a dose-dependent activation of PKC. The particulate PKC activity was significantly increased by 2 nM S1-AII after both short- and long-term incubation. A high concentration of S1-AII (200 nM) caused a translocation of PKC activity from cytosolic to particulate fractions after 10 min incubation with the translocation still observed after 18 hrs of continuous incubation. Sar1-Thr3-angiotensin II (S1-T3-AII), an AII-antagonist, inhibited the effect of S1-AII (20 nM) on PKC activity, suggesting a specific AII receptor-mediated effect. An increase in BAM cell particulate PKC immunoreactivity after 18 hr S1-AII treatment was observed in western-blot analysis of PKC immunoreactive protein (82 kD). The persistent activation of PKC seen in this study is consistent with our hypothesis that PKC may mediate the S1-AII induced increase in the expression of genes encoding proenkephalin and catecholamine synthesizing enzymes in BAM cells.
