Synthesis of Complex Carbohydrates in the Golgi Region, as Shown by Radioautography after Injection of Labeled Glucose

Biochemical work (1, 2) has shown that free glucose is incorporated into mucopolysaccharides and glycoproteins in the course of their synthesis. (The word glycoprotein is used to refer to protein-associated carbohydrates, reference 3.) Little is known, however, about the sites of these syntheses. Kumamoto (4) observed that, after injection of radioactive glucose, many cells, in particular those secreting mucus, became radioactive, presumably due to uptake of glucose into the complex carbohydrates of mucus. However, her work gave no indication of the intracellular site of this synthesis. Attention was drawn to the Golgi zone because it is often stained with the periodic acid-Schiff technique (5) (believed to be specific for glycoproteins, reference 6) and with the colloidal iron technique (7) (believed to stain acid mucopolysaccharides, reference 8). Further evidence was provided by the radioautographic finding that sulfate-S ~s was taken up into the Golgi zone of chondrocytes and of certain mucus-secreting cells (9, 10), indicating that this zone was the site of sulfation of complex carbohydrates. Was the Golgi zone also the site of synthesis of these carbohydrates? In the hope of clarifying the problem, labeled glucose was injected into rats; and radioautographs were prepared of a variety of cells, including those which are active in the elaboration of complex carbohydrates.