Dietary modification of the distribution of 3-hydroxy-3-methylglutaryl coenzyme A reductase and sterol synthesizing activities in the rat small intestine.

The distribution of microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase in the rat small intestine was modified by the type of the diets. The reductase activity in rats fed a commercial non-purified diet (rat chow) was markedly higher in the ileum than in the jejunum, while this pattern was reversed in animals fed a purified diet. Feeding a fat-containing purified diet, in comparison with a fat-free diet, resulted in a significant increase in the activity of the villous reductase. In rats fed a purified diet, the synthesis of digitonin precipitable sterols from [1-14C]acetate in vivo was considerably higher in rats fed a purified diet than in the animals fed a non-purified diet. Although responses to various measurements were not always consistent, the observation that the type of the diet modifies specifically the intra- and inter-tissue distribution of cholesterol synthesizing activity in the intestine strongly stresses the necessity of appropriate sectioning of the tissues, particularly in comparative studies. Also, comparisons of the sterogenesis of the small bowel and liver denote the possibility that intestinal contribution to endogenous cholesterol synthesis is considerably greater than previously estimated, even in the absence of dietary cholesterol.