Effects of plasma cholesterol lowering agents on hepatobiliary lipid metabolism and cholesterol turnover in the rhesus monkey.

The effects of clofibrate, cholestyramine, and neomycin on hepatobiliary lipid metabolism were studied in adult rhesus monkeys in metabolic steady state with intact but exteriorized enterohepatic circulations. Clofibrate (30 mg/kg, id) had no effect on lipid secretion while cholestyramine (150 mg/kg, id) decreased biliary cholesterol secretion rate from 0.19 +/- 0.03 to 0.13 +/- 0.02 mmol/24 h, p less than 0.05. Neomycin (30 mg/kg, id) decreased bile flow from 216 +/- 10 to 191 +/- 7mL/24 h, p less than 0.05, and tended only to decrease bile salt and phospholipid secretion rates. Cholestyramine decreased cholesterol composition from 1.81 +/- 0.22 to 1.30 +/- 0.22 mol %, p less than 0.05, while clofibrate and neomycin had insignificant effects. Cholestyramine and neomycin decreased bile salt pool size from 1 +/- 0.1 to 0.77 +/- 0.15 and from 1.45 +/- 0.16 to 1.13 +/- 0.21 mmol, p less than 0.05, respectively, while clofibrate had no effect. Bile salt synthetic rate was increased only by cholestyramine, i.e., from 0.63 +/- 0.04 to 1.48 +/- 0.26 mmol/24 h, p less than 0.01. Concomitant cholesterol turnover studies revealed that cholestyramine increased the production rate and excretion of cholesterol in the rapidly miscible cholesterol pool and increased the transfer of cholesterol from slow to rapidly miscible pools. Neomycin, on the other hand, decreased the size of the rapidly miscible pool by decreasing production rate without affecting the size of the slowly miscible pool, while clofibrate had insignificant effects.