Supersensitivity of isolated mesenteric arteries to noradrenaline in the long-term experimental diabetic rat.

1 In the present investigation, noradrenaline-induced vascular contractions in isolated rat mesenteric arteries were studied in short and long-term experimental diabetic rats. The diabetic state was induced with streptozotocin (65 mg/kg, i.v.). 2 Long-term diabetic rats were hypertensive when compared to age-matched control rats. In contrast, short-term diabetic rats appeared to be hypotensive when compared to age-matched control rats. 3 Long-term diabetic mesenteric arteries were supersensitive to noradrenaline and developed more contractile force in response to noradrenaline when compared to age-matched control mesenteric arteries. beta-adrenoreceptor antagonism had no effect on the sensitivity of the mesenteric arteries (diabetic and control) for noradrenaline, however, there was an increase in the contractile force developed by these tissues in response to noradrenaline during beta-adrenoreceptor antagonism. 4 alpha-Adrenoreceptor antagonism produced a decrease in the sensitivity of both long-term diabetic and corresponding age-matched control mesenteric arteries. alpha-Adrenoreceptor antagonism had no effect on contractile force developed by long-term mesenteric arteries (diabetic and control) in response to noradrenaline. 5 The present data indicate that long-term experimental diabetes produces a supersensitivity of rat mesenteric arteries to noradrenaline. This phenomenon is dependent upon the duration of the diabetic state. Supersensitivity of the mesenteric arteries to noradrenaline may indicate an increased arterial vascular resistance which may contribute to the observed hypertension.