Expression of hepatic microsomal cholesterol 7 alpha-hydroxylase activity in lean and obese Zucker rats.

Expression of hepatic microsomal cholesterol 7 alpha-hydroxylase activity in lean and obese Zucker rats.

Tang P M; Finkelstein J A; Chiang J Y

Biochemical and biophysical research communications

1988

1988-01

The activity of hepatic microsomal cholesterol 7 alpha-hydroxylase was studied in genetically obese and lean Zucker rats. The liver microsomal cholesterol 7 alpha-hydroxylase activity in fatty Zucker rats (fa/fa) is about 50% to 70% lower than that of the lean (Fa/-) rats of the same sex, when animals were sacrificed at the middle of the dark cycle. When rats were sacrificed at the middle of the light cycle, cholesterol 7 alpha-hydroxylase activity was the same as in the dark cycle in obese rats of both sexes, but was 65% lower in lean rats. However, cholesterol 7 alpha-hydroxylase activity was stimulated by the treatment with cholestyramine in both obese and lean rats. Our results suggested that the diurnal regulation of cholesterol 7 alpha-hydroxylase activity is lost in obese rats but was present under cholestyramine treatment in the genetically obese strain of rats.

Female; Male; Animals; Rats; Sex Factors; Species Specificity; Obesity/*metabolism; Liver/*enzymology; Cholestyramine Resin/pharmacology; Cholesterol 7-alpha-Hydroxylase/*metabolism; Steroid Hydroxylases/*metabolism; Microsomes; Zucker/metabolism

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