Evaluation of cholesterol absorption in rats using markers labeled with stable isotopes. Effect of complete bile diversion

BACKGROUND/AIMS: An easily performed method to measure cholesterol absorption with isotope labeled cholesterol and beta-sitostanol in humans is described. The first aim of the study was to show whether this method can also be used in rats. Secondly, to see whether complete bile diversion results in a complete loss of cholesterol absorption. METHODOLOGY: Cholesterol absorption was evaluated in rats by the constant isotope feeding method using [2H6]cholesterol and [2H4]sitostanol as markers. Fecal samples were analyzed by gas-chromatography/mass spectrometry. RESULTS: In 8 rats with intact enterohepatic circulation of bile acids, cholesterol absorption averaged 61 (3% (SD) (range: 54-69%)). Complete bile diversion was followed by an almost total loss of cholesterol absorption (5.5+/-0.6%, range: 2.4-6.9%, n=7). CONCLUSIONS: The results indicate that deuterated cholesterol and deuterated sitostanol are reliable markers for measurement of cholesterol absorption in rats and that bile acids are essential for cholesterol absorption.