THE EFFECT OF DEXAMETHASONE TREATMENT ON THE EXPRESSION OF THE REGULATORY GENES OF KETOGENESIS IN INTESTINE AND LIVER OF SUCKLING RATS

The influence of the injection of dexamethasone on ketogenesis in 12 d ay old suckling rats was studied in intestine and liver by determining mRNA levels and enzyme activity of the two genes responsible for regu lation of ketogenesis: carnitine palmitoyl transferase I (CPT I) and m itochondrial HMG-CoA synthase. Dexamethasone produced a 2 fold increas e in mRNA and activity of CPT I in intestine, but led to a decrease in mit. HMG-CoA synthase. In liver the mRNA levels and activity of both CPT I and mit. HMG-CoA synthase decreased. Comparison of these values with the ketogenic rate of both tissues following dexamethasone treatm ent suggests that mit. HMG-CoA synthase could be the main gene respons ible for the regulation of ketogenesis in suckling rats. The changes p roduced in serum ketone bodies by dexamethasone, with a profile that i s more similar to the ketogenic rate in the liver than that in the int estine, indicate that liver contributes more to ketone body synthesis in suckling rats. Two day treatment with dexamethasone produced no cha nge in mRNA or activity levels for CPT I in liver or intestine. While mRNA levels for mit. HMG-CoA synthase changed little, the enzyme activ ity is decreased in both tissues.