Newly synthesized hepatic cholesterol as precursor for cholesterol and bile acids in rat bile

Adult, male rats were given simultaneously 3H-mevalonate and 14C-cholesterol on autologous lipoproteins intravenously in barbital anaesthesia. The specific radioactivities of sterols in bile, liver and serum were determined. Newly synthesized hepatic cholesterol was a better substrate for cholic and chenodeoxycholic acid than was cholesterol reaching the liver via plasma lipoproteins. The cholesterol secreted into bile was derived from a pool of liver cholesterol which was in close contact with newly synthesized cholesterol. Specific radioactivity of chenodeoxycholate in bile was higher than that of cholate in bile, both when newly made radioactive cholesterol and when radioactive cholesterol on plasma lipoproteins was the precursor for the labelled bile acids.