Influence of fructose feeding on individual enzymic reactions in the formation and metabolism of bile acids in rat liver homogenates.

1. Rats were maintained for 10 d on a semi-synthetic diet containing 700 g glucose or 700 g fructose/kg. Individual enzymic reactions in bile acid synthesis and metabolism were studied by measuring the 7alpha-hydroxylation of [4-14C]cholesterol, and 12alpha-hydroxylation of 7alpha-[6beta-3H]hydroxy-4-cholesten-3-one, the 26-hydroxylation of 5beta-[7beta-3H]cholestane-3alpha,7alpha-diol and the 6beta-hydroxylation of [3H]lithocholic acid in liver homogenates. 2. The serum cholesterol level was approximately the same in both groups of animals, but the serum triglyceride level was almost twice as high in the fructose-fed rats compared to the glucose-fed rats. 3. The 6beta-hydroxylation of [3H]ithocholic acid was increased by about 20% in the fructose-fed rats compared to the glucose-fed animals. The activities of the other enzymic reactions studied did not differ significantly between the two groups of animals. The findings are discussed in relation to previous knowledge concerning mechanisms regulating triglyceride, pre-beta-lipoprotein and bile acid synthesis.