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

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.

Key-words:

• Dog
• dose-response
• gastric inhibition
• gastric secretion
• histamine
• sympathomimetics