EFFECT OF STIMULATION OF MUCOSAL HCO3- SECRETION ON ACID-INDUCED INJURY TO PORCINE DUODENAL MUCOSA

The effect of stimulation of duodenal mucosal bicarbonate secretion wi th vasoactive intestinal peptide (VIP) on acid-induced damage to the d uodenal mucosa was studied in anaesthetized pigs in which bile and pan creatic juice were diverted from the duodenum. Mucosal damage was quan titatively assessed histologically, and mucosal blood flow was determi ned by means of radioactively labelled microspheres. Compared with pla cebo, intravenous infusion of VIP (500 pmol/kg/h) significantly stimul ated duodenal mucosal bicarbonate secretion (47 +/- 13 versus 249 +/- 53 mu mol/h) without concomitant changes in mucosal blood Bow (51.5 +/ - 7.8 Versus 48.5 +/- 9.1 ml/min/100 g) or arterial bicarbonate concen tration (24.2 +/- 1.1 versus 23.4 +/- 0.9 mM). The same dose of VIP in creased the acid disappearance rate in the duodenum (2.2 +/- 0.14 vers us 3.3 +/- 0.09 mmol/h) and reduced the extent of damage to the duoden al surface (16 +/- 2% versus 7 +/- 2%) during duodenal infusion of 0.0 3 M HCl but not 0.1 M HCl. We conclude that the protection offered by VIP against the small dose of acid is most likely secondary to the eff ect of VIP on mucosal bicarbonate secretion. Thus, this study suggests that duodenal mucosal bicarbonate secretion, independent of mucosal b lood flow, is an integral factor in duodenal mucosal defence.