title: Oxytocin binding sites in lactating rabbit mammary gland.
abstract: Material which specifically binds oxytocin was prepared from a crude preparation of lactating rabbit mammary gland by purification on a sucrose density gradient. On examination of activities of enzyme markers and the molar ratio of cholesterol to phospholipid, this material was considered to be a highly purified plasma membrane fraction. For the determination of specificity and time course of oxytocin binding, a Scatchard plot analysis was carried out for the crude and purified fractions. Dissociation constant (Kd) and binding capacity values were found to be as follows: crude, Kd equals 1.83 X 10(-9) M, capacity equals 670 fmol/mg protein; purified, Kd equals 2.8 X 10(-9) M, capacity equals 1700 fmol/mg protein. Treatment of the purified material with different detergents resulted in loss of all [3H]oxytocin binding capacity. However, preincubation of this material with [3H]oxytocin prior to detergent treatment resulted in solubilization of a receptor-hormone complex. This complex remained in the supernatant even after centrifugation at 210 000 X g for 30 min. Using oxytocin analogs, we have shown this solubilized complex to be oxytocin specific.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000032:analysis; D005260:Female; D007774:Lactation; D008099:Liver / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D010121:Oxytocin / Q000031:analogs & derivatives / Q000378:metabolism*; D010743:Phospholipids / Q000032:analysis; D011092:Polyethylene Glycols / Q000494:pharmacology; D011247:Pregnancy; D011490:Protein Disulfide Reductase (Glutathione) / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*
chemical_list: D010743:Phospholipids; D011956:Receptors, Cell Surface; D011092:Polyethylene Glycols; D010121:Oxytocin; D002784:Cholesterol; D011490:Protein Disulfide Reductase (Glutathione)