The origin of cholesterol in liver, small intestine, adrenal gland, and testis of the rat: dietary versus endogenous contributions.

All mammalian tissues so far examined, with the exception of adult brain, are capable of incorporating acetate carbon into cholesterol (l-5). It has been estimated that man synthesizes in the neighborhood of 1.5 gm. of cholesterol per day, a quantity apparently exceeding that ingested when an ordinary mixed diet is fed (6). According to Chevalier (7), the laboratory rat synthesizes about 43 mg. of cholesterol daily, which is also in excess of that normally ingested by this animal. The significance of synthetic cholesterol was emphasized in a recent report (8) in which it was estimated that as much as 75 per cent of plasma cholesterol is of endogenous origin in rats fed an ordinary diet, and that the endogenous contribution to plasma cholesterol could not be completely suppressed even when the rats received, for 6 weeks, a diet containing 2.0 per cent cholesterol. It would thus appear that endogenous sources must contribute significantly to the cholesterol found in most tissues of animals fed laboratory diets. The present report deals with the relative contributions of dietary and endogenous cholesterol to the composition of cholesterol in four tissues: liver, small intestine, adrenal gland, and testis of rats fed diets containing 0.05 and 2.0 per cent cholesterol. The small intestine and liver are of interest because they are concerned in large measure with the handling of absorbed cholesterol; the two glandular tissues, because they participate in the conversion of cholesterol to steroid hormones.