[Bradykinin receptor and the mechanism of the onset of labor].
Bradykinin (BK) receptor of uterus and chorionic membrane were studied by radioreceptor assay to clarify the role of BK as theta an agent contracting uterine muscle. Basic examination revealed that incubation at 0 degrees C for 45 minutes with [3H] BK in buffer containing 5mM Mg++ was the most suitable condition for receptor-BK binding. BK receptor assay of several kinds of tissue such as pregnant rat uterus, human chorionic membrane, and placenta was done and the following results were obtained. Specific BK receptor existed in human chorionic membrane and in rat uterus. Ultracentrifugation revealed that it was on the plasma membrane (145 f mole./mg protein: The highest binding in the pellet at 10,000 g centrifugation followed by 600 g centrifugation). Association constant (Ka) and maximal binding capacity (MBC) showed the lowest level at 15 days gestation in rat uterus. These seemed to effectively maintain pregnancy by inhibiting uterine contraction. Both Ka and MBC were increased in the uterus of intrapartum rat compared with that of prepartum, but the former was about 45%, and the latter was almost the same as, that of non pregnant rat.
D000818:Animals; D002823:Chorion / Q000032:analysis; D005260:Female; D006801:Humans; D007745:Labor Onset; D007743:Labor, Obstetric; D011247:Pregnancy; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter / Q000032:analysis / Q000502:physiology*; D014590:Uterine Contraction; D014599:Uterus / Q000032:analysis
D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter