Toshimi Mizunuma

Cytochemistry of fat absorption

Publisher Summary After ingestion of a fat-containing meal, dietary lipids are partially hydrolyzed and absorbed into intestinal mucosa. In the mucosa, the hydrolytic products are resynthesized into triglycerides, cholesterol, and phospholipids. The resulting lipids are combined with apoproteins to form intestinal lipoproteins, primarily chylomicrons, and very low-density lipoproteins. The chapter discusses the mechanisms of the absorption of triglyceride—the major source of lipids in the diet. The mechanism of chylomicron secretion from the intestinal absorptive cells into the intercellular space has eluded precise ultrastructural definition. The secretion of nascent chylomicrons is thought to involve exocytosis or the fusion of lipid-laden secretory vesicles with the lateral plasmalemma, resulting in the release of chylomicrons into the intercellular spaces. The chapter provides a general morphology of the rat intestinal epithelial cell. The intestinal epithelial cell is tall and columnar. The apical border is largely covered by an array of regularly spaced microvilli, which may increase the mucosal surface. The basal surface of the cell rests on a thin basement membrane that separates the epithelium from the lamina propria.