Ultracytochemical studies on fat absorption by choline-deficient rats.

Abstract

Marked delay of fat absorption was observed in choline-deficient rats. The morphology of intestinal epithelial cells of choline-deficient rats was examined during fat absorption. By light microscopy, numerous lipid droplets remained in the apical zone of absorptive cells even 3hr after fat feeding. Ultracytochemically, the apical plasma membrane of these cells showed irregular microvilli with bleb formation and the Mg-ATPase and K-NPPase activities in the surface epithelium were decreased. Furthermore, absorptive cells in the choline-deficient state showed reduced Ca-ATPase (myosin ATPase) activity in the terminal web and other filamental bundles in close proximity to secretory vesicles throughout the cytoplasm. These findings were associated with poorly developed, disorganized microfilaments between the intracellular organelles and numerous large lipid droplets throughout the cytoplasm of absorptive cells. These lipid droplets often fused with each other and were large and irregular in shape near the Golgi complex. These observations indicate an altered state of contraction of microfilaments, accounting for impaired intracellular transport and discharge of chylomicrons by the intestine in choline-deficient rats.