Effect of Isoprenaline on Pentagastrin-Stimulated Gastric Acid Secretion in Dogs with Gastric Fistula

Abstract

The purpose of this study was to elucidate the effect of a β₁-adrenoceptor agonist on gastric acid secretion in conscious dogs with gastric fistula. Isoprenaline, a β₁- and β₂-agonist was used alone and in conjunction with selective blockade of β₂- and β₁- receptors. Isoprenaline dose-dependently inhibited the secretory volume and the acidity. The antisecretory effect of isoprenaline was significantly blocked by the β₁-adrenoceptor blocker practolol and by the β₁ + β₂-adrenoceptor blocker propranolol but not by H 35/25, a β₂-adrenoceptor blocker. This indicates that isoprenaline acts on the acid secretion exclusively through β₁-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.

Key-words:

• β-Blocking drugs
• dogs
• dose response
• gastric inhibition
• gastric secretion
• isoprenaline
• pentagastrin