REGULATION OF PHENOBARBITAL-INDUCED FERROCHELATASE MESSENGER-RNA ACTIVITY BY DIBUTYRYL CAMP AND GLUCOSE IN NORMAL AND DIABETIC RAT HEPATOCYTES

The induction of ferrochelatase activity by phenobarbital and its potentiation by dibutyryl cAMP assayed in normal rat hepatocytes are associated with increased activity of ferrochelatase mRNA. Glucose inhibits this stimulatory effect. This inhibition can be reversed with increasing concentrations of dibutyryl cAMP. The inducing effect exerted by phenobarbital on the activity of ferrochelatase mRNA in diabetic hepatocytes is greater than that observed in normal cells. This enhanced response in diabetic rat hepatocytes is neither potentiated by adding dibutyryl cAMP nor repressed by glucose. The absence of a glucose effect persists even when the endogenous cAMP content is lowered to normal levels. The results obtained in this study are consistent with those reported in other published studies of ferrochelatase activity. This adds more experimental evidence to support the concept that ferrochelatase is inducible. The results obtained suggest that ferrochelatase is more susceptible to induction with phenobarbital in diabetic rat hepatocytes than in normal rat hepatocytes.