The effect of a selective beta2-adrenoceptor agonist on
histamine-stimulated gastric acid secretion was studied in conscious
gastric-fistula dogs. A dose-dependent inhibition was found, most pronounced for the lowest doses of
histamine. The inhibition was on the volume, whereas the acidity was unchanged. The pulse rate was increased by the beta2-agonist and by
histamine.
Propranolol prevented the inhibition of
acid secretion as well as the increase in pulse rate.
Practolol had no effect on the inhibition of
acid secretion but reduced the increase in pulse rate. Dose-response experiments with six doses of
histamine and two doses of the beta2-agonist showed unchanged calculated maximal response and an increase in D50. It is concluded that the beta2-agonist inhibits
histamine-induced
acid secretion in the dog, but to a lesser degree that
pentagastrin-induced
acid secretion, as found in earlier experiments. The inhibition follows competitive kinetics, and beta2-receptors are probably involved. The influence of beta2-sympathomimetics on the mechanism of gastric acid secretion is discussed.