Pharmacologic characterization of the oxytocin receptor in human uterine smooth muscle cells

• Published in: British journal of pharmacology 2000-01, Vol.129 (1), p.131-139
• Main Authors: Tahara, Atsuo, Tsukada, Junko, Tomura, Yuichi, Wada, Koh‐ichi, Kusayama, Toshiyuki, Ishii, Noe, Yatsu, Takeyuki, Uchida, Wataru, Tanaka, Akihiro
• Format: Article
• Language: English
• Subjects: Antidiuretic Hormone Receptor Antagonists; Arginine Vasopressin - pharmacology; Binding, Competitive - drug effects; Biological and medical sciences; Calcium - metabolism; Cell Count; Cell Division - drug effects; Cell receptors; Cell structures and functions; Female; Fundamental and applied biological sciences. Psychology; Hormone receptors. Growth factor receptors. Cytokine receptors. Prostaglandin receptors; human; Humans; Hyperplasia - chemically induced; Hyperplasia - pathology; In Vitro Techniques; Kinetics; Ligands; Molecular and cellular biology; Muscle, Smooth - cytology; Muscle, Smooth - drug effects; Oxytocin - analogs & derivatives; Oxytocin - pharmacology; Oxytocin receptor; Receptors, Oxytocin - agonists; Receptors, Oxytocin - antagonists & inhibitors; Receptors, Oxytocin - drug effects; Receptors, Vasopressin - agonists; Second Messenger Systems - drug effects; uterine smooth muscle cells; Uterus - cytology; Uterus - drug effects; Vasoconstrictor Agents - pharmacology; vasopressin receptor
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0702996

[3H]‐oxytocin was used to characterize the oxytocin receptor found in human uterine smooth muscle cells (USMC). Specific binding of [3H]‐oxytocin to USMC plasma membranes was dependent upon time, temperature and membrane protein concentration. Scatchard plot analysis of equilibrium binding data revealed the existence of a single class of high‐affinity binding sites with an apparent equilibrium dissociation constant (Kd) of 0.76 nM and a maximum receptor density (Bmax) of 153 fmol mg−1 protein. The Hill coefficient (nH) did not differ significantly from unity, suggesting binding to homogenous, non‐interacting receptor populations. Competitive inhibition of [3H]‐oxytocin binding showed that oxytocin and vasopressin (AVP) receptor agonists and antagonists displaced [3H]‐oxytocin in a concentration‐dependent manner. The order of potencies for peptide agonists and antagonists was: oxytocin>[Asu1,6]‐oxytocin>AVP= atosiban>d(CH2)5Tyr(Me)AVP>[Thr4,Gly7]‐oxytocin>dDAVP, and for nonpeptide antagonists was: L‐371257>YM087>SR 49059>OPC‐21268>SR 121463A>OPC‐31260. Oxytocin significantly induced concentration‐dependent increase in intracellular Ca2+ concentration ([Ca2+]i) and hyperplasia in USMC. The oxytocin receptor antagonists, atosiban and L‐371257, potently and concentration‐dependently inhibited oxytocin‐induced [Ca2+]i increase and hyperplasia. In contrast, the V1A receptor selective antagonist, SR 49059, and the V2 receptor selective antagonist, SR 121463A, did not potently inhibit oxytocin‐induced [Ca2+]i increase and hyperplasia. The potency order of antagonists in inhibiting oxytocin‐induced [Ca2+]i increase and hyperplasia was similar to that observed in radioligand binding assays. In conclusion, these data provide evidence that the high‐affinity [3H]‐oxytocin binding site found in human USMC is a functional oxytocin receptor coupled to [Ca2+]i increase and cell growth. Thus human USMC may prove to be a valuable tool in further investigation of the physiologic and pathophysiologic roles of oxytocin in the uterus. British Journal of Pharmacology (2000) 129, 131–139; doi:10.1038/sj.bjp.0702996