Comparison of cholesterol turnover by sterol balance and input-output analysis, and a shortened way to estimate total exchangeable mass of cholesterol by the combination of the two methods.

Daily turnover of cholesterol obtained by the balance method was compared to daily input rates calculated by input-output analysis in 43 experiments. The mean value of input rates for kinetic data of 10.1-16.4 weeks' duration (14 experiments) was 1.05 g/day vs. the chemical turnover of 0.94 g/day (difference 10.9 percent). For decay curves of 4.8-9.9 weeks' duration (29 experiments) the mean results were 1.67 g/day vs. 1.31 g/day, respectively (difference 20.1 percent). A combination of the balance method with input-output analysis is proposed to estimate the size of M (minimum value of the total exchangeable mass of cholesterol) in short-term experiments. Using this method, the analysis of curves of 10-12 weeks' duration showed a mean difference of 7.5 percent with the analysis of curves of 50-66 weeks' duration in 17 patients. However, because of considerable variations that can occur in individual cases, it is urged that a standard correction factor not be used, either in estimating turnover data or M from 10-12 weeks' kinetic data; rather, the proposed combined method will alert the investigator to the occurrence of discrepant results.