The effect of secretin on gastric H+ and pepsin secretion and on urinary electrolyte excretion in man.

After an initial 40-min period of gastric suction, the gastric juice was collected for 12 30-min periods from 8 healthy young male students. During the first hour 30-min periods saline alone was infused, whereafter secretin in a dose of 0.05 CU/kg and h was given in the middle four 30-min periods and in a dose of 0.25 CU/kg and h for the final four 30-min periods. Urine was collected in three 2-h portions corresponding to each change of infusion procedure, and blood for determination of plasma secretin by a radioimmunoassay procedure was drawn at hourly intervals. Plasma secretin was unaltered both during the saline infusion and during the infusion of secretin in a dose of 0.05 CU/kg and h but rose during the infusion of 0.25 CU/kg and h. Compared with the mean 30-min output in the initial saline control period, gastrin pepsin secretion rose significantly in the third 30-min period, and gastric H+ output fell significantly in the fourth 30-min period of infusion of secretin in a dose of 0.05 CU/kg and h. During the higher secretin dose gastric output could not be evaluated owing to duodenogastric reflux. Urinary sodium excretion increased only during the infusion of secretin in a dose of 0.25 CU/kg and h, whereas secretin showed no effect on the urinary outputs of water, potassium, and solutes. The results of the present study indicate that secretin may play a physiological role in the regulation of gastric H+ and pepsin secretions, whereas its diuretic effect probably is a pharmacological effect only.