PROTEIN-KINASE-C AND CYP1A1 INDUCTION IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) HEPATOCYTE CULTURE

1. The role of protein kinase C (PKC) in B-naphthoflavone (BNF) induct ion of CYP1A1 in rainbow trout hepatocytes was investigated. 2. Primar y cultures of rainbow trout hepatocytes treated with BNF for 24 hr sho wed an increase in microsomal 7-ethyoxyresorufin-O-deethylase (EROD) a ctivity compared to cells treated with vehicle (DMSO) only. 3. Increas es in EROD activities were proportional to increased concentrations of BNF from 1 to 10 nM reaching a plateau at higher concentrations (20-1 00 nM) of BNF. 4. Western blot analysis using specific antibody (LM4b) against CYP1A1 showed that changes in microsomal CYP1A1 protein paral leled that of EROD activity. 5. The induction of EROD activity by BNF required both protein and RNA synthesis since the process was blocked by both cycloheximide and actinomycin D. 6. Pretreatment of hepatocyte s with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) led to a dose depen dent suppression of BNF-induced EROD activity and CYP1A1 content. TPA alone had no effect on hepatic EROD activity and CYP1A1 protein level. 7. Pretreatment with sn-1,2 didecanoylglycerol, a PKC activator, had no effect on BNF-induced EROD activity in these cells. 8. Pretreatment of cells with staurosporine, a PKC inhibitor, effectively blocked BNF -induced EROD activity. 9. PKC may play a role in the induction of CYP 1A1 gene expression in fish liver by BNF.