The diabetes-induced functional and distributional changes of the alpha 1-adrenoceptor of the abdominal aorta and distal mesenteric artery from streptozotocin-induced diabetic rats

Background: The aim of this study was to evaluate the effect of diabetes on the function and distribution of vascular α₁-adrenoceptors in the abdominal aorta and distal mesenteric artery from streptozotocin (STZ)-induced diabetic rats at the level of the α₁-adrenoceptor subtypes. Methods: Diabetes was induced by a single intravenous injection of STZ (60 mg/kg) in 8 week-old male Sprague-Dawley rats (n = 11). Age-matched normal rats (n = 14) were used as a control group. Four weeks after STZ injection, the tilting-induced change of the mean arterial pressure was recorded. The α₁-adrenoceptor subtypes mediating the contractions of the distal mesenteric artery and abdominal aorta were investigated using the agonist phenylephrine and subtype-selective antagonists that included prazocin, 5-methylurapidil and BMY 7378. The expressions of the α_1-adrenoceptor subtypes of each artery were examined by immunofluorescence staining using the subtype selective antibodies. Results: The recovery of the mean arterial pressure was delayed after positional change in the diabetic rats. Compared with that of the normal rats, the contractile response to phenylephrine was increased in the abdominal aortas and it was decreased in the distal mesenteric arteries in the diabetic rats. In addition, compared with the normal rats, the fluorescent intensity of all the α₁-adrenoceptor subtypes was increased in the abdominal aortas and it was decreased in the mesenteric arteries of the diabetic rats. Conclusions: Diabetes increased the contractility of the abdominal aorta in response to phenylephrine, yet diabetes decreased that of the mesenteric arteries in the STZ-induced diabetic rats. Those results are mainly based on the overall change of the α₁-adrenoceptor, and not on the change of the specific α₁-adrenoceptor subtypes.