Induction of physical dependence by chronic alcohol treatment and enhancement of hepatic metabolism of 7-ethoxycoumarin and subsequent conjugation of its metabolite in perfused rat livers.

Physical dependence to alcohol was induced in rats and the rates of hepatic oxidation of 7-ethoxycoumarin to 7-hydroxycoumarin and of the subsequent conjugation of 7-hydroxycoumarin were studied using isolated perfused livers. Seven to 11.2 g of ethanol per kg body weight per day were given to rats in 2 divided doses at 10 a.m. and at 8 p.m. for 7, 9, 11, and 13 consecutive days. All rats surviving these courses of ethanol administration have demonstrated moderate degrees of withdrawal signs. In the isolated perfused livers obtained from these alcohol dependent rats, 100 microM 7-ethoxycoumarin was infused. The rate of 7-hydroxycoumarin formation was increased from 36 to 50 nmoles per min per g of liver tissue. This increase has occurred without significant changes of the liver weights. With such increase in the rate of mixed function oxidation, greater amounts of the 7-hydroxycoumarin metabolite were conjugated not only to glucuronide (from 4.9 to 6.7 nmoles), but also to sulfate ester (from 27.6 to 42.1 nmoles). Furthermore, a greater percentage of the produced metabolite was conjugated in the ethanol treated rat liver. A high concentration of 7-hydroxycoumarin (100 microM) was also infused in order to determine the effect of chronic alcohol administration on the maximal available rates of conjugation. Results indicated that the maximal rates of conjugation were significantly decreased. However, these decreased conjugation rates were still much greater than the maximal production rate for 7-hydroxycoumarin from the infused 7-ethoxycoumarin, for which the rate of oxidation has been elevated by the chronic ethanol treatment. Thus, the livers obtained from rats chronically treated with alcohol have increased rates for both the initial drug oxidation and the subsequent conjugation, even though the maximal rates of conjugation, per se, are reduced.