THE FATE OF GLYCOGEN IN GRANULAR TUBULE CELLS OF RAT SUBMANDIBULAR GLANDS DURING SECRETORY EVENTS

Glycogen, studied electron microscopically in granular tubule cells by means of the periodic acid-thiocarbohydrazide-silver proteinase techn ique, was found to be scattered abundantly throughout the cytoplasm. P arasympathetic nerve stimulation caused no detectable change in the gl ycogen. Degranulation of the granular tubule cells after either sympat hetic nerve stimulation or cyclocytidine injection caused loss of the glycogen from the cells. Study of tubule cells undergoing secretion in the early stages after cyclocytidine injection indicated that glycoge nolysis was occurring. Glycogen had reaccumulated in the cells within 24 h, before extensive reformation of the secretory granules had occur red, and remained abundant throughout the subsequent granule formation . It is concluded that glycogen provides an important source of energy during secretory degranulation of the granular tubule cells.