Roets E, Burvenich C, Peeters G
Department of Physiology, Faculty of Veterinary Medicine, University of Ghent, Belgium.
Arch Int Pharmacodyn Ther. 1988 May-Jun;293:175-85.
Alpha 2-adrenoceptors on platelet membranes, isolated from "slaughterhouse cows," were characterized by [3H]-rauwolscine binding. There were 30 +/- 3 [3H]rauwolscine sites per platelet, corresponding to 194 +/- 18 fmol/mg protein. These had an equilibrium dissociation constant (KD) of 5.25 +/- 0.56 nM, a Hill coefficient of 1.00 +/- 0.01 (n = 9), and were competed for by adrenergic compounds stereoselectively. The rank order of catecholamines coincided with that expected for alpha 2-adrenoceptors. Ki-values for inhibition of specific [3H]rauwolscine binding by 7 agonists and 6 antagonists were in the same range as previously observed in teat tissue. It is therefore concluded that quite similar [3H]rauwolscine binding sites were identified and characterized in both bovine teats and platelets. Direct comparison of binding characteristics between alpha 2-adrenoceptors from teat tissue and platelets of the same "primiparous cows," revealed no difference in binding affinity, although a significant higher platelet receptor number was noted in the platelets (platelets: 353 fmol/mg protein; teat tissue: 91 fmol/mg protein; n = 10).
从“屠宰场奶牛”分离的血小板膜上的α2 - 肾上腺素能受体通过[3H] - 萝芙辛结合进行表征。每个血小板有30±3个[3H]萝芙辛结合位点，相当于194±18 fmol/mg蛋白质。这些位点的平衡解离常数（KD）为5.25±0.56 nM，希尔系数为1.00±0.01（n = 9），并且被肾上腺素能化合物立体选择性竞争。儿茶酚胺的竞争顺序与α2 - 肾上腺素能受体预期的顺序一致。7种激动剂和6种拮抗剂抑制特异性[3H]萝芙辛结合的Ki值与先前在乳头组织中观察到的范围相同。因此得出结论，在牛乳头和血小板中鉴定并表征了非常相似的[3H]萝芙辛结合位点。对同一“初产奶牛”的乳头组织和血小板中的α2 - 肾上腺素能受体之间的结合特性进行直接比较，发现结合亲和力没有差异，尽管在血小板中观察到显著更高的血小板受体数量（血小板：353 fmol/mg蛋白质；乳头组织：91 fmol/mg蛋白质；n = 10）。
