alpha1-Adrenoceptor subtypes mediating the contraction of arteries in spontaneously hypertensive rats

1. This study was undertaken to determine which alpha1-adrenoceptor (AR) subtypes were involved in the activation of the femoral artery and the aorta by norepinephrine (NE) in spontaneously hypertensive rats (SHR). 2. Negative log EC50 values and maximum responses of NE-induced contraction of the SHR femoral artery were unchanged and increased, respectively, compared with those of Wistar-Kyoto (WKY) rats. 3. Contractile responses of the SHR aortas to NE were similar to those of the normotensive tissues. 4. Schild plot data for alpha1-AR antagonists indicated that alpha1-AR in the aorta were predominantly alpha1H subtype. In the femoral artery, because Schild plots for bunazosin had slopes of less than 1.0, there were alpha1H (or alpha1C) and alpha1L subtypes. 5. The alpha1-AR subtype in the aorta was essentially identical to the alpha1H subtype in the femoral artery. alpha1-AR subtypes mediating contraction in the SHR blood vessels were identical to those in the WKY tissues.