Effect of isoprenaline on pentagastrin-stimulated gastric acid secretion in dogs with gastric fistula.

The purpose of this study was to elucidate the effect of a beta 1-adrenoceptor agonist on gastric acid secretion in conscious dogs with gastric fistula. Isoprenaline, a beta 1- and beta 2-agonist was used alone and in conjunction with selective blockade of beta 2- and beta 1-receptors. Isoprenaline dose-dependently inhibited the secretory volume and the acidity. The antisecretory effect of isoprenaline was significantly blocked by the beta 1-adrenoceptor blocker practolol and by the beta 1 + beta 2-adrenoceptor blocker propranolol but not by H 35/25, a beta 2-adrenoceptor blocker. This indicates that isoprenaline acts on the acid secretion exclusively through beta 1-receptors. Dose-response experiments with five logarithmically increased doses of pentagastrin and one dose of isoprenaline showed unchanged calculated maximum response and an increase in half-maximum acid response. It is concluded that the inhibitory effect of isoprenaline on gastric acid secretion is of competitive or uncompetitive type.