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Laboratory of Nutrition Chemistry, Kyushu University School of Agriculture 46-09, Fukuoka 812, Japan
The effects of dietary fats on intestinal 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity were studied in rats. Animals were fed experimental diets ad libitum for 713 d then killed in the morning for the determination of the reductase activity in an epithelial cell homogenate. When corn oil was the source of dietary fat, the specific activity of jejunal reductase depicted a biphasic pattern in response to dietary fat level with a peak activity when the diet contained 10% fat (by weight) whereas the specific activity of ileal reductase was independent of the fat level. Reductase activities were apparently independent of the degree of saturation of dietary fat (safflower oil, olive oil, lard and tallow) when each was fed as 10% of the diet. Both jejunal and ileal reductase activities were higher when trilaurin was fed than when other saturated fats (tricaprylin, trimyristin, tripalmitin and tristearin) were fed. The jejunum synthesized more cholesterol than the ileum. There was no significant correlation among the reductase activity, cholesterol content of the epithelial cells and the rate of fat absorption, suggesting a complex regulatory mechanism.
KEY WORDS: HMG-CoA reductase dietary fat jejunum ileum
1 This study was supported in part by a Grant-in-Aid for Scientific Research (No. 547104) from the Ministry of Education, Science and Culture.
2 To whom reprint requests should be addressed.
Manuscript received 19 October 1984. Revision accepted 29 March 1985.