Response of rats with chronic gastric fistulas to subcutaneous injections of histamine, ICI-50123, and insulin

Effect of intraduodenally administered histamine on gastric acid secretion in rats and guinea pigs

We examined the effect of histamine administered intraduodenally as well as subcutaneously or intravenously on the gastric acid secretion in rats and guinea pigs, using a newly devised cannula. Intraduodenally administered histamine dihydrochloride caused a significant dose-dependent increase in the gastric acid secretion in rats. The maximal acid secretion, which corresponded to that after subcutaneous (20 mg/kg) or intravenous (10 mg/kg/hr) administration of histamine, was observed within 30 min after intraduodenal administration (40 mg/kg). The plasma concentrations of histamine determined 30 min after intraduodenal, subcutaneous, and intravenous administration of histamine were nearly the same. Pretreatment with aminoguanidine sulfate (diamine oxidase inhibitor) at 30 mg/kg significantly increased the gastric acid secretion caused by intraduodenal histamine. The gastric acid secretion stimulated by intraduodenal histamine was significantly inhibited by cimetidine, pirenzepine, and omeprazole, but remained unchanged with tripelennamine. Intraduodenal histamine (20 mg/kg) also maximally stimulated the gastric acid secretion in guinea pigs. The response was comparable to that with subcutaneous histamine (1 mg/kg). We conclude that intraduodenal histamine has the ability to stimulate gastric acid secretion in both rats and guinea pigs.

Dose response relationships of insulin hypoglycaemia and gastric acid in man

Fourteen studies of gastric acid secretion in a basal hour and in the two hours after a single intravenous injection of soluble insulin (0.01 to 0.40 units/kg) were performed in a healthy man. The peak acid output after insulin (measured as the two consecutive 15-minute samples giving the highest acid output) was significantly correlated with the lowest concentration of blood glucose, the fall in blood glucose, the rate of fall of blood glucose, and the maximum fall of blood glucose in any 15 minutes. Peak acid outputs after insulin were similar over the range 0.1 to 0.2 units/kg, and greater than at lower or higher doses. These results are contrary to the accepted assumption that insulin-stimulated acid secretion is an ;all-or-none' phenomenon. They support instead the hypothesis that insulin hypoglycaemia provides a quantitative glycopenic stimulus producing quantitative vagal acid response. Extreme hypoglycaemia, below about 15 mg/100 ml of blood glucose, inhibits insulin-stimulated acid secretion.