Different secretory responses of periinsular and other acini in the rat pancreas after pilocarpine injection.

Histological, histochemical, and electron microscopical investigations of the rat pancreas, one to five hours after pilocarpine injection (4 mg in 1 ml normal saline solution), showed different secretory responses in periinsular and apoinsular acinar cells. The responsiveness to parasympathetic stimulation is markedly retarded and weakened in the periinsular area. It is supposed that the halo phenomenon is related not only to an inhibition of the secretion, but also to a longer lasting synthesis of zymogen granules. The insular hormones, glucagon and insulin, which are possibly locally enriched by insulo-acinar capillary anastomoses or by diffusion, may be involved in the regulation of activity in the periinsular cells.