Characterization of beta-adrenergic receptors in the rat vas deferens using [3H]-dihydroalprenolol binding.

The beta-adrenergic antagonist, [3H]-dihydroalprenolol ([3H] DHA), binds to membranes prepared from the rat vas deferens in a specific and saturable manner. Scatchard and Hill plot analysis indicates a single class of binding sites with no evidence of cooperative interactions. The specific binding sites have a high affinity (Kd = 0.3 nM) and a maximal occupancy estimated to be 460 fmoles [3H]-DHA bound/g wet tissue weight. Beta-adrenergic agonists and/or antagonists inhibit [3H]-DHA binding to rat vas deferens membranes in a stereospecific manner and with a relative order of potency expected for beta-adrenergic receptors of the beta2 subtype. The receptor affinities of various beta-adrenergic antagonists in the rat vas deferens determined using inhibition of [3H]-DHA binding correlated with their receptor affinities determined physiologically using antagonism of isoproterenol-induced inhibition of neurogenic contractions in-vitro.