CONTRACTILE AND RELAXING ACTIVITY OF ARTERIAL SMOOTH-MUSCLE FROM STREPTOZOTOCIN-DIABETIC RATS

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 30  (2) , 283-299
Abstract
Contractures induced by 10-4 M phenylephrine (PE) and 70 mM KCl and their relaxation by 10-2 M theophylline (theo) were observed in aortae isolated from untreated and insulin-treated streptozotocin-diabetic rats for 12 wk after the induction of diabetes. Diabetes consistently caused an average decrease of 40% in the PE and K-contractures. Treatment of diabetic animals with 2.0-3.5 U of Neutral Protamine Hagedorn (NPH) insulin/day partially prevented diabetes-induced decreases in the PE contractures while completely preventing them in the K-contractures. Relaxation of the PE-contracture, which was more susceptible to theo than was the K-contracture in control tissues, was not affected by untreated or insulin-treated diabetes until 12 wk after the induction of diabetes. While in vivo insulin treatment did not reverse diabetes-induced decreases in the theo-induced relaxation of the PE contracture, it did prevent the diabetes-induced increase in the relaxation of the K-contracture which was observed after 4 wk. While the mechanisms involved in mediating the PE and K-contractures are inhibited by diabetes, insulin is more effective at preventing the effects of diabetes on the K-contracture and its relaxation than on the induction and relaxation of the PE-contracture.