IDENTIFICATION OF BETA-ADRENOCEPTOR SUBTYPES IN BOVINE OVARIAN AND MYOMETRIAL CELL-MEMBRANES

Beta-adrenoceptor (beta-AR) concentrations were measured in the ovary and in the myometrium of 36 adult Friesian cows using a radiometric as say. The beta-AR content in both tissues was determined using the high ly specific antagonist (-) [H-3] CGP 12177 and the amounts of beta-AR subtypes were discriminated in the presence of highly selective unlabe lled ligands (CGP 20712A, ICI 118 551, CGP 25827A). Scatchard analysis revealed a good linearity and K-d values suggested the existence of h igh affinity beta-adrenergic sites in the bovine genital tract Total b eta-AR concentrations in the ovary and in the myometrium were, respect ively, 87 +/- 7 (SEM) and 240 +/- 27 fmol mg(-1) of membrane protein. beta(2)-AR concentrations were significantly higher (P<0.01) in the ov ary (66 +/- 5) and the myometrium (180 +/- 29) than those of beta(1)-A R (21 +/- 4 and 60 +/- 5, respectively). Significant differences (P<0. 05) were also to be found between high affinity state beta(2)-AR and l ow affinity beta(2)-AR concentrations, but their values correlated neg atively in the two different tissues. Natural and synthetic agonists i nhibited (-)[H-3]CGP 12177 binding to beta-AR in the following order o f potency: (-)isoproterenol > (+/-)clenbuterol greater than or equal t o(-)adrenaline much greater than much greater than(-)noradrenaline, wh ereas synthetic antagonists inhibited binding in the following order o f potency: (-)propranolol much greater than(+/-) ICI 118 551 much grea ter than much greater than(+/-)CGP 20712A.