Preparation of [24,25-³H]cholesterol. Oxidation in man as a measure of bile acid formation

In order to devise a convenient method for measuring the rate of formation of bile acids from cholesterol in man, [24,25-³H]cholesterol was prepared by catalytic tritiation of desmosterol where the Δ⁵-unsaturation was protected by conversion to the 3α,5α-cyclosterol-6-methyl ether. It was shown that tritium in the purified labeled sterol was located exclusively in the side chain. Measurements of ³H₂O and the specific activity of plasma cholesterol at timed intervals up to 96 hours after administration of the tracer to three subjects afforded values for cholesterol oxidation (equals bile acid formation) in good agreement with accepted figures for bile acid formation determined by other techniques.