Effects of experimental diabetes on the responsiveness of rat aorta.

1. Vascular responsiveness was examined in aortic ring preparations, with or without endothelium, from rats with experimental diabetes induced by streptozotocin and from vehicle-treated (control) rats. 2. There were no significant differences between diabetic tissues and control tissues in the responsiveness to the vasoconstrictors noradrenaline, 5-hydroxytryptamine and KCl, and to the vasodilators sodium nitroprusside, isoprenaline and acetylcholine. 3. When maximum contractions to vasoconstrictors was expressed relative to tissue weight, maximum contractions were significantly greater in diabetic tissues. 4. When expressed in terms of the KCl contraction, there were no significant differences between diabetic and control tissues in the maximum contraction to vasoconstrictors. 5. These results demonstrate that diabetic-induced changes in vascular responsiveness, if any, do not occur at the receptor level.