[Characterization of beta-2 adrenergic receptors in the human uterine artery]

The actions of the hexoprenaline, salbutamol and terbutaline on adrenalin-induced effects in the human artery were studied in vitro. The human uterine artery has a two-part response to adrenalin: The first, rapid (phasic component), and the second, slow and sustained (tonic component). Both beta-2 stimulators relax the tonic component and reduced the amplitude of the phasic component. The depressor effect of the responses to adrenalin is reduced in the presence of butoxamine and intensified in the presence of caffeine. These results suggest the existence on the human uterine artery of beta-2 adrenergic receptors acting as mediators of smooth muscle relaxation, and suggest also that the mechanism of this relaxation is most likely cAMP dependent.