IMPAIRED DUODENAL BICARBONATE SECRETION IN DIABETIC RATS - SALUTARY EFFECT OF NITRIC-OXIDE SYNTHASE INHIBITOR

We previously reported the impaired HCO3- secretion and the increased mucosal susceptibility to acid in the duodenum of streptozotocin (STZ) -induced diabetic rats. In this study, we investigated the salutary ef fect of the NO synthase inhibitor L-NAME (NG-nitro-L-arginine methyl e ster) on these changes and compared it with those of insulin. Animals were injected streptozotocin (STZ: 70 mg/kg, ip) and used after 1, 3-4 , and 5-6 weeks of diabetes with blood glucose levels of > 300 mg/dL. Under urethane anesthesia the HCO3- secretion was measured in the prox imal duodenal loop using a pH-stat method and by adding 10 mM HCl L-NA ME (20 mg/kg x 2) or insulin (4 units/rat) was administered sc for 4-5 weeks, starting 1 week after STZ treatment. The duodenal HCO3- secret ory responses to various stimuli such as mucosal acidification (10 mM HCl for 10 min), 16,16-dimethyl prostaglandin E-2 (dmPGE(2): 10 mu g/k g, iv), and vagal stimulation (0.5 mA, 2 ms, 3 Hz) were significantly decreased in STZ-treated rats, depending on the duration of diabetes. Repeated administration of L-NAME, starting from 1 week after STZ trea tment, significantly reduced blood glucose levels toward normal values and restored the HCO3- responses to various stimuli in STZ rats, the effects being similar to those observed after supplementation of insul in. Diabetic rats developed duodenal lesions after perfusion of the du odenum with 150 mM. HCl for 4 h, but this ulcerogenic response was sig nificantly inhibited by the repeated treatment with L-NAME as well as insulin. We conclude that L-NAME is effective in ameliorating hypergly cemic conditions in STZ-diabetic rats, similar to insulin, and restore s the impaired HCO3- secretion and the increased mucosal susceptibilit y to acid in diabetic rat duodenums.