Effects of pilocarpine treatment and of electrical stimulation of the vagus nerve on the rat parathyroid gland, with special reference to the alteration of storage granules

Effects of pilocarpine treatment and of electrical vagal stimulation on the rat parathyroid were studied ultrastructurally. The number of type I storage granules with a narrow halo (NSG-I) and that of type II storage granules having a wide halo (NSG-II) were calculated. After pilocarpine treatment, NSG-I gradually decreased and reached a minimum at 30 min; in contrast, NSG-II gradually increased and reached a maximum at 20 min, but thereafter it slightly decreased and instead vacuolar bodies increased. Excluding these alterations, the ultrastructure of parenchymal cells showed no remarkable changes. Electrical vagal stimulation furthermore confirmed these results. Acid phosphatase activity was occasionally found in storage granules of both types in control and experimental rats. It was concluded that storage granules normally may be transformed from type I into type II and finally into vacuolar bodies as a result of hydrolysis, and that these processes may be accelerated by parasympathetic stimulation.