REGULATION OF RAT ALCOHOL-DEHYDROGENASE BY CYCLIC-AMP IN PRIMARY HEPATOCYTE CULTURE

Alcohol dehydrogenase (ADH) is enhanced separately by epinephrine and by glucagon in primary rat hepatocyte culture. This study determined w hether cyclic AMP, a common mediator for some of the actions of the ab ove hormones, increases ADH. Administration of theophylline, a cyclic AMP phosphodiesterase inhibitor which increases endogenous cyclic AMP, in a dose of 100 mg/kg to rats for 5 days, increased ADH activity. Di butyryl cyclic AMP (10 mu M) added to primary hepatocytes in culture i ncreased ADH mRNA and ADH activity at 12 and 24 h, respectively, after its addition. The increase in ADH mRNA was preceded by an increase in the expression of C/EBP beta mRNA and in C/EBP beta protein. Dibutyry l cyclic AMP, in transient transfection experiments of primary rat hep atocyte culture, activated an ADH promoter gene construct containing t he C/EBP binding site, but failed to activate a construct containing a 4-bp mutation at this site. These results show that cyclic AMP induce s ADH and suggests that this effect is mediated by C/EBP beta binding to the C/EBP site, The previously demonstrated induction of ADH by epi nephrine and glucagon may be mediated by a common pathway via an incre ase in cyclic AMP. (C) 1995 Academic Press, Inc.