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 assay. The beta-AR content in both tissues was determined using the highly specific antagonist (-) [3H]CGP 12177 and the amounts of beta-AR subtypes were discriminated in the presence of highly selective unlabelled ligands (CGP 20712A, ICI 118 551, CGP 25827A). Scatchard analysis revealed a good linearity and Kd values suggested the existence of high affinity beta-adrenergic sites in the bovine genital tract. Total beta-AR concentrations in the ovary and in the myometrium were, respectively, 87 +/- 7 (SEM) and 240 +/- 27 fmol mg-1 of membrane protein. beta 2-AR concentrations were significantly higher (P < 0.01) in the ovary (66 +/- 5) and the myometrium (180 +/- 29) than those of beta 1-AR (21 +/- 4 and 60 +/- 5, respectively). Significant differences (P < 0.05) were also to be found between high affinity state beta 2-AR and low affinity beta 2-AR concentrations, but their values correlated negatively in the two different tissues. Natural and synthetic agonists inhibited (-) [3H]CGP 12177 binding to beta-AR in the following order of potency: (-)isoproterenol > (+/-)clenbuterol > or = (-)adrenaline >> >> (-)noradrenaline, whereas synthetic antagonists inhibited binding in the following order of potency: (-)propranolol >> (+/-)ICI 118 551 >> >> (+/-)CGP 20712A.
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Department of Animal Pathology, University of Turin, Italy.
Badino
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Novelli
A
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Canese
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MG
Girardi
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C
D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D002462:Cell Membrane / Q000737:chemistry; D005260:Female; D009215:Myometrium / Q000737:chemistry*; D010053:Ovary / Q000737:chemistry*; D011869:Radioligand Assay; D018342:Receptors, Adrenergic, beta-1 / Q000032:analysis*; D018343:Receptors, Adrenergic, beta-2 / Q000032:analysis*
D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2