Dietary Influences on the Hepatic MixedFunction Oxidase System in the Rat After Portacaval Anastomosis

Studies were undertaken to determine the influence of diet on the hepatic mixed-function oxidase system in rats after portacaval anastomosis. Male rats fed either a cereal-based or purified diet underwent portacaval anastomosis. Weight gain after surgery was highly dependent on the diet. Because rats fed the cereal-based diet weighed 50% less at 4–5 wk after portacaval shunt surgery than unoperated controls fed the same diet, pair-fed unoperated controls were also studied. Rats fed the purified diet grew normally after shunting and therefore studies with this diet did not require pair-fed controls. Shunted rats fed the cereal-based diet had lower liver weights, hepatic microsomal protein concentrations, ethylmorphine N-demethylase, aniline hydroxylase, and cytochromes P₄₅₀ and b₅ when compared with corresponding values in unoperated controls fed the same diet ad libitum; comparisons with pair-fed controls indicated that decreased intake of the cereal-based diet could account for part but not all of the changes seen after portacaval anastomosis. It was shown in rats fed the purified diet that sham operation had no effect on the mixed-function oxidase system, whereas portacaval anastomosis resulted in reduced liver weight, microsomal protein, ethylmorphine N-demethylase, aniline hydroxylase, and cytochrome P₄₅₀. In comparing shunted rats fed the two types of diet, in contrast with the effects of these diets in normal rats, these hepatic microsomal mixed-function oxidase system components were generally lower in the shunted rats fed the cereal diet. It is concluded that although decreased mixedfunction oxidase activity occurs after portacaval anastomosis in the rat, the diet can have an additional substantial influence. Dietary influences on drug oxidations may be an important consideration in drug therapy after portacaval anastomosis.