Localization of Cholesterol Esterase and Cholesterol in Mucosal Fractions of Rat Small Intestine.

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Abstract
Summary A modified procedure for brush border preparation has been developed which gives 90–100% yields of invertase activity in the brush border. It was determined that the esterifying and hydrolytic activities of cholesterol esterase are concentrated in the supernatant fraction of the mucosa as opposed to the brush border. Further fractionation of the mucosal cells into nuclei and cell debris, mitochondria, microsomes, and soluble fraction, and assay of these fractions for esterase activity demonstrated that 60–66% of the esterase activity of the whole homogenate was in the soluble fraction. The remaining activity was distributed among the other fractions. The data suggest that esterification of cholesterol occurs in the mucosal cell rather than in the brush border. Cholesterol levels in rat intestinal wall, intestinal mucosa, and mucosal subcellular fractions are also reported.