title: Biosynthesis and transport of glycoproteins in the small intestinal epithelium of rats. I. Developmental change and effect of hypophysectomy.
abstract: The biosynthesis and intracellular transport of glycoproteins in duodenal absorptive cells of intact rats at 6 and 24 days and hypophysectomized rats at 24 days of age were studied after 20 min intralumenal pulse-labeling of D-[3H]galactose, L-[3H]fucose, or D-[3H]mannose. Autoradiographic studies showed that the incorporation of sugars increased significantly in intact rats between 6 and 24 days. When rats were hypophysectomized at 6 days of age, the intestinal epithelium at 24 days incorporated D-[3H]galactose at a level significantly lower than that of intact rats at 24 days. Hypophysectomy also interfered with the developmental increase in D-[3H]mannose, but not in L-[3H]fucose, incorporation. Biochemical study indicated that the radioactivity in the lipid-free acid-precipitable glycoproteins in the intestine of 24-day-old intact rats at 20 min after D-[3H]galactose injection was 129% and 97% higher than that in 6-day-old rats and in 24-day-old hypophysectomized rats, respectively. The patterns of intracellular transport of newly synthesized galactosylated or fucosylated glycoproteins in all animal groups were similar; the labeled glycoproteins were initially present in the Golgi and were transported through the smooth endoplasmic reticulum to either the lateral membrane or the brush-border membrane within 60 min after the injection of labeled sugars. The proportion of labeled glycoproteins that migrated to the brush-border membrane, however, increased about twofold in the intact rats between 6 and 24 days of age at 60-240 min after D-[3H]galactose injection. Hypophysectomy interfered with developmental increase in the transport of glycoproteins from the apical cytoplasm to the brush-border membrane. It was concluded that the incorporation of monosaccharide precursors into glycoproteins and the proportion of newly synthesized galactosylated or fucosylated glycoproteins transported to the brush-border membrane increase during postnatal development. The developmental changes are regulated, at least partially, by the pituitary gland.
mesh_terms: D000818:Animals; D001692:Biological Transport; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D005643:Fucose / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D007016:Hypophysectomy; D007421:Intestine, Small / Q000254:growth & development* / Q000378:metabolism / Q000648:ultrastructure; D008358:Mannose / Q000378:metabolism; D008854:Microscopy, Electron; D008871:Microvilli / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D006023:Glycoproteins; D005643:Fucose; D008358:Mannose; D005690:Galactose