Gastric secretory conditions and plasma gastrin levels in rats after prolonged treatment with cimetidine.

Effects of 4 weeks of treatment with oral cimetidine, 100 mg/kg twice daily, on gastric secretion and plasma gastrin levels were studied in rats. Pylorus ligation-induced and pentagastrin-stimulated gastric secretions were little changed at days 1, 3, and 10 after cessation of cimetidine treatment as compared to the controls. Histamine-stimulated acid secretion was significantly higher in the cimetidine-treated group than in the controls at day 3 after cimetidine treatment but was unchanged at days 1 and 10. A single oral administration of cimetidine at 100 mg/kg significantly increased plasma gastrin levels 4 hr after the treatment in refed rats but not at 2 and 8 hr later. Plasma gastrin levels significantly decreased at days 3 and 10 after cessation of cimetidine treatment as compared to the controls. Thus, while prolonged treatment with cimetidine induces a transient increase in response of parietal cells to histamine and a reduction of food-stimulated gastrin release, it does not seem to induce other appreciable changes in gastric secretion.