The localization of thiamine pyrophosphatase activity in the acinar cells of stimulated and non-stimulated sublingual glands of the rat.

The distribution of thiamine pyrophosphatase (TPPase) activity in the acinar cells of the rat sublingual gland has been studied at various stages of the secretory cycle following stimulated secretion. The rats were stimulated to secrete by an intraperitoneal injection of isoproterenol and pilocarpine. In non-stimulated glands, TPPase activity is detected mainly in 3--4 cisternae at the inner concave side of the Golgi complex and in some adjacent condensing vacuoles as in other cells. In the acinar cells 1 to 2 h after stimulation, however, reaction product for the same enzyme activity is detected in the cisternae at the outer aspect, as well as the inner aspect, of the Golgi complex and even in the cisternae of the endoplasmic reticulum (ER). About 4 h after stimulation, TPPase activity becomes concentrated in 3--4 cisternae at the inner concave side of the Golgi complex as in the acinar cells under non-stimulated conditions. Morphological observations of the acinar cells 1 to 2 h after the stimulation have indicated that the reorganization of the Golgi complex and ER is a major event which occurs at this stage. It is possible that this cellular event is related to the occurrence of TPPase activity in those sites which normally show negative reaction in non-stimulated state.