Relationships between cholesterogenesis, microsomal sterols and HMG-CoA reductase in the perfused rat liver.

The relationships between cholesterogenesis and the activity of HMG-CoA reductase of microsomes prepared with or without sodium fluoride, and between changes of cholesterogenesis and microsomal sterols were studied in the isolated rat liver perfused with or without oleic acid in the presence of AY-9944. AY-9944 inhibits the conversion of 7-dehydrocholesterol, measured colorimetrically as "fast-acting" sterols, the cholesterol, measured colorimetrically as "slow-acting" sterols. The level of "fast-acting" sterols is used to estimate cholesterogenesis and changes in microsomal sterols. It was observed that the activity of HMG-CoA reductase of microsomes prepared with or without fluoride reflects the relative changes in cholesterogenesis of the perfused livers. In addition, the amount of "fast-acting" and "slow-acting" sterols in microsomes correlates with increases in the activity of HMG-CoA reductase and cholesterogenesis.