EFFECTS OF PYRILAMINE ON SECRETIONS OF GASTRIC ACID AND GASTRIN AFTER LONG-TERM ACID SUPPRESSION IN RATS

摘要

Long-term acid suppression is known to induce hypergastrinemia, but the underlying reasons why there is no increase in acid secretion, so-called acid rebound, after cessation is still being widely debated. Acid secretion is known to be regulated by many factors, and long-term acid suppression may result in the introduction of other regulatory factors. Histamine H_1 and H_2 receptor subtype are reported to be located on gastrin-immunoreactive cells(G cell). This study investigates the effects of pyrilamine (an H_1 receptor antagonist) on gastric acid and gastrin secretions in rats after 4-week acid suppression. Famotidine (H_2 receptor antagonist 15 mg/kg/day p.o.) was administered in drinking water over a four week period. On the 3rd, 5th and 7th day after cessation of famotidine treatment, the gastric juice pH, acid output, and serum gastrin level were measured in rats, 5 hours after pylorus-ligation, with or without pretreat-ment of pyrilamine (50 mg/kg, i.p.). If administered, pyrilamine pretreated was given prior to 30 minutes before pylorus-ligation. After the cessation of famotidine, the gastric juice pH, acid output, and serum gastrin level were not significantly different from those of the control group. However, pretreatment of pyrilamine significantly increased the acid output and serum gastrin level in the famotidine-treated group, but not in the control group. These results suggest that gastric acid and gastrin secretions become inhibited by the H_1 receptor after long-term treatment with H_2 receptor antagonist.