Free versus esterified sterol levels in the livers of Abcg8+/+, Abcg8+/- and Abcg8-/- mice. Sterol contents of liver extracts of 12-week-old female mice fed a regular chow diet, determined by GC analysis show that the majority of sterols in all genotypes are unesterified. Esterified cholesterol (panel a) remains relatively constant for each genotype. However, no esterified sitosterol in the livers from Abcg8+/+ and Abcg8+/- mice and very little from Abcg8-/- mice was detected (panel b). Small amounts of esterified campesterol were detected in each of the genotypes (panel c).