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The localization and characterization of bradykinin B2 receptors in sheep uterus was carried out using a radiolabelled B2 receptor ligand, 3,4-hydroxyphenypropionyl-D-Arg0-[Hyp3,Thi5,D-++ +Tic7,D-Oic8] bradykinin (HPP-HOE140). Competition of the radioligand, [125I]HPP-HOE140, from membrane preparations of anoestrus sheep uterus by bradykinin agonists and antagonists revealed the presence of high- and low-affinity binding sites with ligand specificity typical of the bradykinin B2 receptor. Using in vitro autoradiography on tissue sections, intense binding was visible over the superficial epithelial layer of the endometrium and inner third of the myometrium of anoestrus sheep uterus. Bradykinin B2 receptors in the myometrium were down regulated in pregnant sheep uterus. We demonstrate that binding studies using [125I]HPP-HOE140 offer high sensitivity and specificity for characterization, quantitation and localization of the bradykinin B2 receptors in tissues and offers new information on uterine bradykinin B2 receptors. |
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