Glycoprotein secretion in the mouse submandibular gland as revealed by radioautography after L-3H-fucose injection

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Abstract
Glycoprotein secretion in the mouse submandibular gland was investigated by light microscope radioautography of semi-thin sections after the administration of L-3H-fucose. The incorporation of the precursor in the acini was negligible. 3H-fucose was taken up in the paranuclear region of the cells lining the intercalated, secretory, striated and excretory ducts. This labeling pattern was interpreted as addition of the precursor to glycoproteins within the Golgi apparatus. Incorporation in the intercalated duct was restricted to the cells with fine cytoplasmic granules. The glycoproteins synthesized by the intercalated and secretory ducts were transported to the saliva by the secretion granules. It is assumed that the glycoproteins synthesized in the striated and excretory ducts are plasma membrane glycoproteins which seem to renew continuously. Quantitation of the radioautographs supplied data concerning the incorporation of 3H-fucose into newly synthesized glycoproteins as well as the renewal of the labeled macromolecules in each duct.