Migration of Glycoprotein from Golgi Apparatus to Cell Coat in the Columnar Cells of the Duodenal Epithelium

A layer of carbohydrate material appears at the surface of a variety of mammalian cells (1) and is particularly abundant at free surfaces such as the striated border of the columnar cells of the intestine (2). In electron micrographs of intestinal cells, this material appears as a discrete coating covering the tips and sides of the microvilli (3). From the various histochemical tests applied (3-I0), it has been concluded that this "cell coat" consists of glycoprotein rich in acidic residues (I, 9). After incubation of cat intestine with a labeled precursor of complex carbohydrates (glucose-SH) followed by EM radioautography, Ito (l l) observed radioautographic reaction first over the cytoplasm of columnar cells and, after 1 hr, over the cell coat of the free surfaces. In this laboratory, by means of light microscopic radioautography, after injection of galactose-3H into young rats, label was localized, at early time intervals, to the Golgi region of duodenal columnar cells, and later traced