HYPOXIA INHIBITS GASTRIC-EMPTYING AND GASTRIC-ACID SECRETION IN CONSCIOUS RATS

This study examines the effects of hypoxia on the gastric function in conscious rats which adapted to a meal-feeding schedule, that allowed free access to a high protein (HP) diet (550 g casein/kg diet, Exp. 1, 2 and 4), a normal protein (NP) diet (200 g casein/kg diet, Exp. 3) o r a nonpurified rat (NPR) diet (Exp. 5 and 6) for 4 h every day for 2 wk. In Exp. 1, after 4 h of consuming the HP diet, rats were exposed t o 7.6 or 10.5% O-2 normobaric hypoxia. Hypoxia delayed the excretion o f urinary urea for 12 h. In Exp. 2 and 3, when rats were exposed to 7. 6% O-2 after 4 h of consuming the HP diet and exposed to 10.5% O-2 aft er 4 h of consuming the NP diet, respectively, a significant delay in gastric emptying was found in the hypoxic rats. In Exp. 4, when rats w ere exposed to 7.6 O-2 hypoxia after 4 h of eating the HP diet, the pl asma gastrin concentration in the 7.6% O-2 hypoxic rats was 2.3-fold t hat of the normoxic rats after 6 h of hypoxia. Furthermore, when rats that did not consume any HP diet on the day of the experiment were exp osed to 7.6 or 10.5% O-2 hypoxia, the plasma gastrin concentration was higher in both hypoxic groups than in the normoxic group after 3 and 6 h of hypoxia. In Exp. 5, rats that were not fed the NPR diet on the day of study were exposed to 7.6 or 10.5% O-2 hypoxia for 3 h after py lorus ligation. Hypoxia inhibited the secretion of gastric acid and el evated the plasma gastrin concentration. In Exp. 6, unfed rats that ha d been consuming the NPR diet were: exposed to 7.6% O-2 hypoxia for 3 h after pylorus ligation and were orally administered HCl. The rise of the gastrin concentration due to hypoxia was completely inhibited by oral HCl. These results demonstrate that hypoxia inhibits gastric empt ying and gastric acid secretion and that the inhibitory effect of hypo xia on gastric acid secretion stimulates gastrin release through posit ive feedback regulation.