Effects of a β2-Sympathomimetic on Histamine-stimulated Gastric Acid Secretion in Dogs

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Abstract
The effect of a selective β2-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 β2-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 β2-agonist showed unchanged calculated maximal response and an increase in D50. It is concluded that the β2-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 β2-receptors are probably involved. The influence of β2-sympathomimetics on the mechanism of gastric acid secretion is discussed.