title: Study of oxytocin receptor in human myometrium using highly specific 3H-labeled oxytocin.
abstract: A highly specific tritium labeled oxytocin (3H-OT) was synthesized utilizing the method of catalytic substitution of halogen for hydrogen. The specific activity of 3H-OT was 19 Ci/mM and the biologic activity was 350 U/mg, which was sufficient for the OT radioreceptor assay. The maximum % uptake of 3H-OT in the human myometrium was observed in 20,000 X g pellets under the optimal conditions of pH 7.4, at 20 degrees C and the incubation time of 90 min and it was augmented in the presence of Mn++. It was observed from the Scatchard plot, that the binding site of OT in the human myometrial specimens was a single type within the range of OT concentration of 0.4 nM to 1.6 nM. The dissociation constants (Kd) and the number of binding sites (NBS) showed a relative increase as gestation advance. The apparent Kd of term pregnancies was 1.25 X 10(-9) M regardless of the presence or absence of labor pains, while the NBS of term pregnancies with and without labor pain was 1.2 X 10(-12) and 4.7 X 10(-12) moles/mg, protein, respectively.
mesh_terms: D005260:Female; D006801:Humans; D007553:Isotope Labeling; D009215:Myometrium / Q000378:metabolism*; D010121:Oxytocin / Q000378:metabolism*; D011247:Pregnancy; D011956:Receptors, Cell Surface / Q000378:metabolism*; D014316:Tritium; D014599:Uterus / Q000378:metabolism*
chemical_list: D011956:Receptors, Cell Surface; D014316:Tritium; D010121:Oxytocin