Abstract: | A portion of the minute chylomicrons less than 75 nm in diameter are transcytosed from
the extravascular tissue into the subepithelial blood capillaries (sBC) in the villous
apices of the rat jejunum. However, the details of the transportation mechanism have not
been clarified. In this study, the endothelial receptor involved in the transportation of
minute chylomicrons into the sBC’s lumina was immunohistochemically and
histoplanimetrically examined in intestinal villi of the rat jejunum. Immunopositivity for
very low density lipoprotein (VLDL) receptor was detected on the luminal and basal
surfaces of the endothelial cells of sBC in approximately 68% of those apices of jejunal
villi that possessed numerous chylomicrons in the lamina propria, while VLDL receptor was
detected on the endothelial cells of sBC in only approximately 8% of intestinal villi that
possessed few or no chylomicrons in the lamina propria. No immunopositivity for LDL
receptor was detected in the sBC of all intestinal villi. These findings suggest that VLDL
receptor is expressed by the endothelial cells of the sBC in conjunction with the filling
of the lamina propria of jejunal villi with many chylomicrons produced by the villous
columnar epithelial cells and that the VLDL receptor mediates the transportation of minute
chylomicrons, maybe VLDL, into the subepithelial portal blood from the extravascular
tissue of the rat jejunal villi. |