Feed-back control of cholesterol synthesis in partially hepatectomized rats

Partial hepatectomy caused a marked stimulation of cholesterol and fatty acid syntheses without affecting serum total cholesterol, total phospholipid and triacylglycerol concentrations of rats so far examined 48 h after the operation. Serum free cholesterol level, however, was increased by the treatment and the ratio of lysophosphatidylcholine to phosphatidylcholine was concomitantly decreased, suggesting the impairment of serum lecithin: cholesterol acyltransferase activity. The lipid content in the liver, especially triacylglycerol and ester cholesterol, was increased markedly by the operation. Feeding of a high cholesterol diet which elevated serum cholesterol and phospholipid levels to the partially hepatectomized rats, accelerated the accumulation of hepatic triacylglycerol and ester cholesterol by the partial hepatectomy. The weight of the regenerating liver was not influenced by cholesterol feeding, which suggested that cholesterol feeding did not inhibit the regeneration mechanism of the liver. The increase of cholesterol synthesis after partial hepatectomy was inhibited by cholesterol feeding. Therefore, it is conceivable that the negative feed-back control of cholesterol synthesis is induced by cholesterol feeding under the stimulated cell divisions of the liver after partial hepatectomy. It is suggested from the present data that a large amount of the cholesterol which is necessary for cell growth can be taken up from serum, when serum cholesterol concentration is high.