Cholesterol oxidation in primates by simultaneous sterol balance and breath analysis

Six female adult rhesus monkeys and baboons with exteriorized enterohepatic circulations were simultaneously assessed following [26-14C]cholesterol pulse labeling by 14CO2 breath analysis and combined isotopic and chromatographic sterol balance during metabolic steady state. Bile acid synthesis and/or secretion were compared with 14CO2 breath analysis of cholesterol oxidation during short term physiological changes, and with total bile acid diversion and feedback inhibition, and biliary tract obstruction. Cholesterol oxidation by breath analysis compared closely with acidic sterol losses during steady-state conditions (145.6 +/- 23.9 vs 144.6 +/- 24.4 mg/24 h) and was sensitive enough to detect changes resulting from diurnal variation and fasting. The 14CO2 test detected inhibition of bile acid synthesis consequent to bile acid feedback (355 +/- 32 to 88 +/- 31 mg/24 h, P less than 0.001) or biliary tract obstruction (158 +/- 27 to 60 +/- 28 mg/24 h, P less than 0.05) but underestimated increased synthesis induced by acute bile diversion (245 +/- 24 vs. 868 +/- 104 mg/24 h, P less than 0.01 at 24 h). Insignificant 14C was detected by carcass analysis following cessation of exhaled 14CO2.