Hyperreactivity of contractile response in gastric fundus smooth muscle from rats with diabetes induced by streptozotocin.

To understand the effects of diabetes on functions of gastric fundus smooth muscle and the underlying mechanisms, we examined the responses to acetylcholine and KCl in gastric fundus of rats with diabetes (3, 6, 12 weeks) induced by streptozotocin (60 mg/kg, i.v.). The contractile responses to the two agonists increased significantly in gastric fundus preparations isolated 6 and 12 weeks after the onset of diabetes, compared to those in tissues from control rats. Influx of Ca2+, induced by 10(-5) M acetylcholine and 60 mM KCl, increased significantly in gastric fundus isolated 6 weeks after the onset of diabetes. Insulin treatment from 3 to 6 weeks after the onset of diabetes restored the responsiveness of gastric fundus to agonists to control levels. The results indicate that changes of both receptor-operated and voltage-dependent Ca2+ channels contribute to hyperreactivity of contractile responses in gastric fundus of diabetic rats.