Effect of diabetes on microvascular responses in mouse mesentery

Mice 8 weeks old were made diabetic with streptozotocin. Their mesenteric arterioles were studied 4-8 weeks later and their responses compared with those of arterioles in control mice. The responses to the dilators acetylcholine and papaverine and to the constrictor prostaglandin F2 alpha were identical in diabetics and controls whether the changes in diameter were expressed as a percent of baseline diameter or in absolute units (microns). Diabetics had significantly smaller responses than controls, to the constrictors norepinephrine and serotonin. However the effect of diabetes on the response to norepinephrine may have been a spurious consequence of expressing constrictions as a percent of slightly differing resting diameters, since the difference became statistically insignificant when constrictions were expressed in absolute units as microns. The reduced response to serotonin remained significant no matter how constriction was expressed. This result, together with a similar finding in an earlier study of diabetes which used much smaller cerebral vessels, suggests that reduced vascular responses to serotonin may be associated with streptozotocin diabetes of relatively recent onset in mice. The reason for this relatively selective impairment of vasomotor response remains obscure, as does the reason for the spared responses to the other vasoactive agents we tested.