Lipid metabolism in the development of cholesterol gallstones in hamsters. III. The effect of dietary cholesterol on its biliary concentration and lithogenesity.

The effect of dietary cholesterol on the lithogenesity of bile in female hamsters was investigated. Biliary and serum lipids and serum lipoproteins of the hamsters fed with the normal diet supplemented with 1% cholesterol for 10, 20 and 30 days were analyzed. The synthesis rate of phospholipids and triglycerides were determined with (l-14C) palmitate incorporated into these lipids in the livers of the animals. The biliary cholesterol output slightly but significantly increased with a small and temporary increase in phospholipids 20 and 30 days after feeding the cholesterol diet. But these animals failed to show a significant change in the total and individual bile acids. Though the lithogenic index (Holzbach) gradually increased in accordance with the above change in the biliary lipid composition, it stayed far below the saturation point (1. 0) even 30 days after feeding the cholesterol diet, not causing the gallstone formation in the animal gallbladder. The striking increase in serum lipids including total cholesterol, phospholipids and triglycerides, and serum lipoproteins was, on the other hand, observed so shortly as 10 days after the cholesterol diet feeding. The cholesterol diet feeding also produced the increase in the synthesis of phospholipids and triglycerides contributing to the fatty acid composition of biliary phospholipids. These results suggest that dietary cholesterol brings about the increase in the biliary cholesterol output but that phospholipids synthesized in the liver maintain the lithogenesity far below the saturation point in the normal female hamsters. 141