Changes in the somatostatin, substance P and vasoactive intestinal polypeptide content of the gastrointestinal tract following streptozotocin-induced diabetes in the rat.

Rats with streptozotocin-induced diabetes of 10 weeks' duration showed significant changes in the total content of somatostatin, substance P and vasoactive intestinal polypeptide in the stomach and small intestine compared with control animals. An increase (p less than 0.05) in the concentration and total content of gastric somatostatin and a decrease (p less than 0.05) in the concentration and content of gastric substance P were seen in the streptozotocin-treated rats. The increase in the vasoactive intestinal polypeptide (VIP) content (54%, p less than 0.05) and the decrease in the substance P content (35%, p less than 0.05) of the gut may contribute to the impaired intestinal motility observed in animals with experimentally produced diabetes. Both the diabetogenic effect of streptozotocin and the changes in regulatory peptide concentrations were prevented by injection of nicotinamide before streptozotocin suggesting that the changes did not arise from a non-specific toxic effect of streptozotocin upon gastrointestinal neurones and/or endocrine cells.