Homogeneity of beta-adrenoceptors on bovine teat muscles.

Bovine teat beta-adrenergic receptors were investigated with binding studies using 3H-dihydroalprenolol (DHA) as ligand. Inhibition of 3H-DHA-binding by beta 1-(betaxolol, atenolol, practolol) and beta 2-(zinterol, fenoterol, ICI 118551) selective drugs resulted in monophasic displacement curves with Hill coefficients close to 1.0. Computer assisted analysis of these curves did not reveal the presence of more than one class of binding sites. These data suggest that the beta-receptor sites present in bovine teat walls are of the beta 2-subclass.