The influence of chronic experimental diabetes on contractile responses of rat isolated blood vessels.

The influence of experimental diabetes induced by streptozotocin on responses of rat isolated aortae and portal veins to noradrenaline, 5-hydroxytryptamine, and KCl was examined 7, 100, 180, and 360 days after the onset of diabetes. No significant changes in reactivity were seen 7 days after the onset of diabetes. After 100 days aortae from diabetic rats were supersensitive (defined as a significant increase in the pD2 value) to noradrenaline. However, 180 days after the onset of diabetes, the sensitivity of diabetic aortae to noradrenaline was not significantly different from control, while the responsiveness (defined as the maximum developed tension divided by cross-sectional area of aorta) to 5-hydroxytryptamine was reduced. A generalized increase in both the sensitivity and responsiveness of diabetic aortae to all three agonists was observed after 360 days of diabetes. In contrast, no changes in either the sensitivity or the responsiveness of portal veins to noradrenaline, 5-hydroxytryptamine, or KCl could be detected at any time after the onset of diabetes. These results indicate that changes in vascular reactivity can be detected with increasing duration of experimental diabetes. However, these changes do not follow a consistent pattern and are not seen in all parts of the vasculature.