Anatomical heterogeneity of the intestinal mucosa and cholesterol homeostasis. A review of studies with normal and genetically hypercholesterolemic (RICO) Rat.

Quantitative data on cholesterol movements in mucosa cell as a function of its localization in the small intestine have been obtained in normocholesterolemic (SW) or genetically hypercholesterolemic (RICO) rats. Bile cholesterol absorption is greater and more proximal than dietary cholesterol absorption, both taking place mainly in the top cells of the duodenum or the proximal jejunum. Esterification of cholesterol also takes place mainly in the villus cells, while cholesterol synthesis is predominantly carried out in the crypt cells of the proximal duodenum and distal ileum. Cholesterol exchanges, which replace half of the cell cholesterol through the cell life, can be estimated at 3-4%.h-1 between plasma and mucosa cells, according to its location, i.e. 12-25 micrograms.h-1 (per mg cell DNA). In comparison, the cholesterol HDL or LDL uptake appears to be very low (0.02-0.06 and 0.2-0.6 microgram.h-1, respectively). Compartmentalization of cholesterol metabolism in the enterocyte can be suggested by different experimental data. The turnover of newly synthesized cholesterol is about 2-fold lower than that of exogenous (dietary) cholesterol.