A fluorescent cholesterol analog traces cholesterol absorption in hamstersand is esterified in vivo and in vitro

The fluorescent cholesterol analog 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl )amino)-23, 24-bisnor-5-cholen-3 beta-ol (fluoresterol) was characterized a s a tool for exploring the biochemistry and cell biology of intestinal chol esterol absorption, Hamsters absorbed fluoresterol in a concentration- and time-dependent manner, with an efficiency of about 15-30% that of cholester ol, Fluoresterol absorption was blocked by compounds known to inhibit chole sterol absorption, implying that fluoresterol interacts with those elements of the normal pathway for cholesterol absorption on which the inhibitors a ct, Confocal microscopy of small intestinal tissue demonstrated that fluore sterol was taken up by absorptive epithelial cells and packaged into lipopr otein particles, suggesting a normal route of intracellular trafficking. Up take of fluoresterol was confirmed by biochemical analysis of intestinal ti ssue, and a comparison of [H-3]cholesterol and fluoresterol content in the mucosa suggested that fluoresterol moved through the enterocytes more rapid ly than did cholesterol, This interpretation was supported by measurements of fluoresterol esterification in the mucosa, Four hours after hamsters wer e given fluoresterol and [H-3]cholesterol orally, 44% of the fluoresterol i n the intestinal mucosa was esterified, compared to 8% of the [H-3]choleste rol, Caco-2 cells took up 2- to 5-fold more [H-3]cholesterol than fluoreste rol from bile acid micelles, and esterified 21-24% of the fluoresterol but only 1-4% of the [H-3]cholesterol. Thus fluoresterol apparently interacts w ith the proteins required for cholesterol uptake, trafficking, and processi ng in the small intestine.