Mast cells and gastric secretion in the rat

Gastric secretion of acid was measured in adult rats deprived of solid food for 48 hr. In control animals, values were obtained for the residual content of acid in the stomach, indicative of the rate of basal secretion, and for the quantities of acid secreted in 30 min following injections of histamine, pentagastrin, insulin and compound 48/80. The same measurements were made in groups of rats treated for 5 days with compound 48/80 (a regime which depleted the whole body of mast cells) and for 3 days with dexamethasone (which selectively depleted the gastric mucosa of mast cells). The content of residual acid was depressed to one third of the control value in the 48/80-treated rats, but the additional secretion due to histamine, pentagastrin or insulin was unaffected. A secretory response to a single injection of compound 48/80 could not be obtained in rats depleted of mast cells. In the dexamethasone-treated rats, the residual level of acid was increased to 1-5 times the control value, but the magnitudes of the responses to secretogogues were unchanged. It is concluded that basal secretion of acid into the stomach of the rat is stimulated by histamine derived from mast cells throughout the body, those of the gastric mucosa having no special significance in this respect. Mast cells are not involved in the mediation of the secretagogue actions of exogenous histamine, pentagastrin and insulin, but the present results do not preclude the participation of histamine from sources other than mast cells in the process of gastric secretion.