Measurement of bile acid synthesis in man by release of14CO2 from [26-14C]cholesterol: Comparison to isotope dilution and assessment of optimum reference cholesterol specific activity |
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Authors: | John C Mitchell Bradford G Stone William C Duane |
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Affiliation: | (1) Department of Medicine, VA Medical Center, 1 Veterans Drive, 55417 Minneapolis, MN;(2) University of Minnesota, 55417 Minneapolis, Minnesota |
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Abstract: | Bile acid synthesis can be measured as release of14CO2 from 26-14C]cholesterol divided by cholesterol specific activity, but this method has not been validated in human subjects. We made
twelve comparisons of this CO2 method to standard isotope dilution in six normal subjects and found a mean discrepancy of 6%. Linear regression analysis
of one value with respect to the other revealed a correlation coefficient of 0.83 (P<0.001), a Y-intercept close to zero (−4.98)
and a slope close to 1 (1.06), suggesting good correspondence between the two methods. To assess the potential for error arising
from use of serum cholesterol to estimate specific activity of cholesterol used for bile acid synthesis, we compared synthesis
measured using serum free cholesterol specific activity to that measured using bile cholesterol specific activity, which is
known to be near isotopic equilibrium with the precursor pool used for bile acid synthesis. Synthesis calculated in these
two ways differed by less than 10%. The data indicate that the CO2 method using either serum or bile cholesterol specific activity provides a valid estimate of bile acid synthesis in man. |
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