Hepatic 3-Hydroxy-3-Methylglutaryl CoA Reductase Activity in Germfree Rats

Germfree rats have a reduced fecal excretion of bile acids and neutral steroids and higher levels of serum and liver cholesterol compared with conventional rats. In accordance with this finding the 7α hydroxylation of cholesterol, which is the rate limiting step in the conversion of cholesterol to bile acids, tends to be decreased in germfree rats. The rate determining step in the biosynthesis of cholesterol is the formation of mevalonic acid from HMG CoA (3 hydroxy 3 methylglutaryl CoA). Techniques have been described for determining the activity of the HMG CoA reductase. In order to further clarify the mechanisms behind the differences in cholesterol metabolism between germfree and conventional rats, it was considered of importance to investigate the cholesterol synthesis.