Relaxant and beta 2-adrenoceptor blocking activities of (+/- )-, (+)- and (-)-pindolol on the rat isolated aorta

The KCl contracted rat aorta is relaxed by procaterol, (+/- )-, (+)- and (-)-pindolol. The relaxations to procaterol, but not to (+/- )-pindolol, were prevented by ICI 118,551 at 10(-6) M. The relaxations to (+/- )-pindolol are, therefore, not due to beta-adrenoceptor agonism. At 10(-7) M ICI 118,551, (+/- )-, (+)- and (-)-pindolol were beta 2-adrenoceptor antagonists as they inhibited the relaxant responses of the aorta to procaterol.