The purpose of this study was to evaluate the gender-related changes in the function and distribution of α₁-adrenoceptors in the distal mesenteric artery of streptozotocin (STZ)-induced diabetic rats at the level of α₁-adrenoceptor subtypes.

Diabetes was induced by intravenous injection of STZ in a dose of 60 mg/kg through the tail vein in 8 week-old male or female Sprague-Dawley rats (n = 13/group). Age-matched normal rats (n = 15) were used as a control group. Four weeks after STZ injection, the change in mean arterial pressure caused by a 45° tilting was recorded. The α₁-adrenoceptor subtypes mediating contractions of the distal mesenteric artery were investigated using the agonist, phenylephrine as well as subtype-selective antagonists including prazocin, 5-methylurapidil, and BMY 7378. The expression of α₁-adrenoceptor subtypes of each artery was examined by immunofluorescence staining and western blotting using subtype selective antibodies.

Compared with normal male rats, the contractile response to phenylephrine was decreased in the distal mesenteric artery in normal female rats. Moreover, a decrease in contractile force was observed in STZ-induced diabetic rats compared with age-matched controls. Western blotting revealed that there was the difference between normal male and female rats in manifestation of the α_1D-adrenoceptor. In STZ-induced male and female diabetic rats, all α₁-adrenoceptor subtypes were decreased in distal mesenteric arteries, compared with normal rats.

There was the gender-related functional difference of α₁-adrenoceptors in normal rats. In both male and female rats, diabetes decreased the contractile response in mesenteric arteries, which might be caused by the overall change in α₁-adrenoceptor.