Secretion in the B-cells of islets of Langerhans as demonstrated by zinc staining.

Intact islets of Langerhans were isolated from Wistar rats by means of vital fixation, microdissection and development of the metal sulfides formed with Timms reagent. In such intact islets, the beta-granules and the cell organelles can be shown up well electron microscopically. The endocrine pancreas tissue of normal rats contains a relatively constant average of 715 densely structured granules per 100 microns2. After administration of sulfonylurea, the number of (less dense) granules is reduced to 125 (in adipose animals 115) granules per 100 microns2. Besides empty 'sacs', large-vesicle Golgi apparatus and ballooned forms of the endoplasmic reticulum occur.