TABLE 1.

Estimated Number of Exchangeable Hydrogens in Cholesterol

	Cholesterol Isotopomer Distribution (%)
Group	M1	M2	Water Labeling (% Excess)	n
Theoretical	29.9	4.4	—	—
Control	30.2 ± 0.1	4.4 ± 0.1	—	—
CF diet	48.4 ± 2.4	17.0 ± 1.7	2.9 ± 0.1	27.0 ± 1.0
HC diet	39.8 ± 2.0	10.8 ± 1.4	2.9 ± 0.2	25.2 ± 1.0

The mass isotopomer profile of cholesterol and the labeling of plasma water were determined using GCqMS. The theoretical isotope distribution profile for cholesterol was determined using the isotope calculator reported at http://www.sisweb.com/mstools/isotope.htm. In all cases, the abundance of the M0 isotopomer of cholesterol is 100% (data not shown), and the abundance of the M1 and M2 isotopomers of cholesterol are expressed as a percentage of M0. The number of exchangeable hydrogens (n) was determined from the M2/M1 labeling ratio of cholesterol. Water labeling was determined as described in Materials and Methods. Data are mean ± SEM (five mice per group).