In hepatomas, the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-controlling enzyme in cholesterol biosynthesis, is not normally suppressed by cholesterol. To examine the biochemical mechanism of this loss of feedback control of cholesterol synthesis, a comparison was made of the properties of 3-hydroxy-3-methylglutaryl coenzyme A reductase after solubilization and partia...

Hepatic cholesterol metabolism was examined in 27 Swedish patients with cholesterol gallstone disease and in 13 patients free of gallstones operated for roentgenographically suspect polyps in the gallbladder. All 40 patients underwent cholecystectomy, and a liver biopsy and gallbladder bile were obtained at surgery. The cholesterol saturation of gallbladder bile was significantly higher in pati...

Among nine strains of rat, two were found that responded to phenobarbital treatment with increased activity of hepatic cholesterol 7 alpha-hydroxylase. This effect was maximal after 2-3 days of treatment and was then reduced. Interestingly the increased cholesterol 7 alpha-hydroxylase activity was associated with increased activity of hepatic HMG-CoA reductase in the two responding strains but ...

BACKGROUND AND OBJECTIVES Gamma-oryzanol (gamma-OR) is a unique mixture of triterpene alcohol and sterol ferulates present in rice bran oil. Hypocholesterolemic activity of gamma-OR has been reported in various animal and human studies. However, the mechanisms for this hypocholesterolemic activity of gamma-OR remain unclear. Therefore, the aim of this in vitro study was to examine the effect of...

In hepatomas, the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-controlling enzyme in cholesterol biosynthesis, is not normally suppressed by cholesterol. To examine the biochemical mechanism of this loss of feedback control of cholesterol synthesis, a comparison was made of the properties of 3-hydroxy-3-methylglutaryl coenzyme A reductase after solubilization and partia...

A simple and rapid mixed-phase method for the quantitative assay of 3-hydroxy-3-methylglutaryl (HMG)CoA reductase and a procedure for the efficient reactivation of Mg-ATP-inactivated microsomal HMG-CoA reductase by potato acid phosphatase are described. The mixed-phase assay entails the direct addition of the acidified, deproteinized incubation mixture to a toluene-based scintillation fluor. Th...

Growth hormone (GH) has an important role in the regulation of hepatic LDL receptor expression and plasma lipoprotein levels. This investigation was undertaken to characterize the effects of GH on hepatic cholesterol and bile acid metabolism in the rat. In hypophysectomized (Hx) rats, the activities of the rate-limiting enzymes in cholesterol and bile acid biosynthesis, 3-hydroxy-3-methylglutar...

The effect of i.v. injection of mevalonate on the activity of microsomal 3-hydroxy-3-methylglutaryl Coenzyme A reductase was studied in livers from non-tumor-bearing rats and in host liver and hepatomas from rats bearing transplantable Morris hepatoma 7800. We confirmed that a single bolus injection of 100 mg of mevalonate in non-tumor-bearing male rats caused a 90% inhibition of hepatic 3-hydr...