Characterization of .BETA.-adrenoceptors in the dog saphenous vein.

Abstract

In vitro experiments were carried out on strips of dog saphenous vein to characterize .beta.-adrenoceptors mediating relaxation. Four .beta.-adrenoceptor agonists, isoproterenol, salbutamol, procaterol and .alpha.-(3,4,5-trimethoxyphenethylaminomethyl)-3,4-dihydroxybenzylalcohol hydrochloride (T-1583), all produced concentration-dependent relaxation of venous strips contracted by 10-6 M methoxamine. These 4 drugs behaved as full agonists. In producing venous relaxation, procaterol was .apprx. 2.5 times more potent, and salbutamol and T-1583 were 7 and 98 times less potent than isoproterenol, on a molar basis. The concentration-relaxation response curves to the 4 agonists were shifted in a parallel way to the right by (tert-butylamino-3-ol-2-propyl)oximino-9 fluorene hydrochloride (IPS 339), a selective .beta.2-adrenoceptor antagonist, and by practolol. pA2-values for IPS 339 against the 4 agonists were all nearly 11.0, whereas those for practolol were all nearly 5.7. .beta.-Adrenoceptors mediating relaxation in the dog saphenous vein are predominantly of the .beta.2 type.