Glycoprotein containing vesicles in the surface epithelial cells of the ascending colon of the rat

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Abstract
Recently, radioautographic studies have shown that cell coat glycoproteins are transported to the cell surface by vesicles both in the amoeba (Flickinger, '75) and in the epithelial cells of the ascending colon of the mouse (Michaels and Leblond, 1976). In the current morphological and cytochemical study of the surface epithelial cells of the rat ascending colon, it is shown that filamentous material, resembling the cell coat, is contained in saccules toward the mature face of the Golgi apparatus and in vesicles close to the apparatus and near the terminal web. The vesicles are limited by a unit membrane composed of asymmetric osmiophilic leaflets and similar to the plasma membrane. When stained by the periodic acid‐chromic acid‐silver methenamine technique, silver was precipitated on the cell components containing the filamentous material indicating the presence of glycoproteins. Narrow invaginations from the cell surface that may correspond to vesicles undergoing exocytosis were also positive for glycoproteins. The distribution of the filamentous material that was glycoprotein positive parallels the pathway followed by material that had been found to be labeled with a tritiated glycoprotein precursor (3H‐fucose) in the epithelial cells of the ascending colon of the mouse. It is suggested that the system of vesicles in the rat colon cells is acting in a manner similar to the vesicles in the mouse cells to transport cell coat glycoproteins from the Golgi apparatus to the cell surface.