Alpha1A- and alpha1B-adrenoceptors are the major subtypes in human saphenous vein.

In this study we analyzed the different alpha1-adrenoceptor (AR) subtypes present in human saphenous vein (HSV) using reverse transcription polymerase chain reaction (RT-PCR), DNA-DNA hybridization analysis and functional affinities for alpha-AR antagonists. DNA-DNA hybridization analysis of RT-PCR amplification products confirmed the presence of alpha1A- and alpha1B-ARs, and low levels of alpha1D-AR in HSV. The functional results showed: (1) prazosin, the selective alpha1-AR antagonist, phentolamine, the alpha1- and alpha2-ARs antagonist, WB 4101 and 5-MU, the selective alpha1A-AR subtype antagonists were potent, competitive antagonists of noradrenaline (NA)-induced contraction (pA2 values of 11.03, 8.06, 9.02 and 8.34, respectively). (2) Alpha1-AR-induced contraction was sensitive to the alkylating effects of CEC (the alpha1B and alpha1D-AR subtypes antagonist) and (3) The selective alpha1D-AR subtype antagonist BMY displayed low affinity (pA2 values of 6.44). This indicates that the contractile response of the HSV to alpha1-AR-induced is predominantly mediated by both alpha1A and alpha1B-AR subtypes. This was also supported by the good relationship between pA2 values from the present study and reported binding affinities (pKi) values of various alpha1-AR subtype antagonists with cloned human alpha1A- and alpha1B-AR subtypes (r=0.89 and r=0.98, respectively), but not the alpha1D-AR subtype (r=0.67). Our results indicate that alpha1A- and alpha1B-ARs are the main functional and expressed receptor subtypes in HSV.