Enhancement of Peptone-Induced Gastric Acid Secretion in Streptozotocin-Induced Diabetic Rats

Abstract

We compared the acid secretory response to peptone in normal and streptozotocin-induced diabetic rats. Animals were injected with streptozotocin and used after 5 weeks of diabetes with blood glucose levels of >350 mg/dl. Under urethane anesthesia, 2 ml peptone solution (2–8%) was instilled in the stomach through an acute fistula every 30 min. Peptone increased acid secretion in a concentration-dependent manner in normal rats, the maximal response being obtained at 8%. Likewise, the increased acid response was observed in diabetic rats, yet the maximal response observed at 497o was significantly greater than that in normal rats. In both cases, this response was inhibited potently by famotidine as well as YM-022 (a CCKB antagonist) and partially inhibited by atropine. Peptone increased luminal histamine and plasma gastrin levels in both normal and diabetic rats, and the former response was significantly greater in diabetic animals. The altered acid secretion and histamine output in diabetic rats were reverted by insulin treatment. Pentagastrin- but not histamine-induced acid secretion was also increased in diabetic rats. We conclude that peptone-induced acid secretion is increased in diabetic conditions. This phenomenon is insulin-dependent and associated with an enhanced release of histamine but not with an increased sensitivity of the parietal cells.