Alterations in aortic and tail artery reactivity to agonists after streptozotocin treatment.

In the present study, responses to various agonists in thoracic aorta and tail artery strips, obtained from 4-week streptozotocin (STZ)-treated rats and age-matched controls, were studied. Responses in aorta obtained from diabetic animals to the alpha-agonists, norepinephrine (NE), and methoxamine (MOX), to calcium (Ca2+) and potassium (K+) were found to be depressed relative to control tissue. Responses in tail artery however, were found to be different. While responses to K+ were decreased and to Ca2+ unchanged, tail artery strips obtained from diabetic animals were found to be supersensitive to both alpha-agonists relative to control tissue. Another observed difference between the two tissues was in their catecholamine content. While induction of diabetes did not alter catecholamine levels in the aorta, a significant decrease was produced in the tail artery, relative to control tissue levels. Our results indicate that inherent differences (such as the degree of innervation) may contribute to the differential responses observed in the two tissues studied. They further suggest the possible involvement of alterations in calcium utilization in aorta and the development of postjunctional supersensitivity in tail artery obtained from STZ-treated animals.