Comparison of vasopressin binding sites in human uterine and vascular smooth muscle cells

• Published in: European journal of pharmacology 1999-07, Vol.378 (1), p.137-142
• Main Authors: Tahara, Atsuo, Tsukada, Junko, Ishii, Noe, Tomura, Yuichi, Wada, Koh-ichi, Kusayama, Toshiyuki, Yatsu, Takeyuki, Uchida, Wataru, Tanaka, Akihiro
• Format: Article
• Language: English
• Subjects: Binding Sites; Biological and medical sciences; Cell physiology; Cell receptors; Cell structures and functions; Female; Fundamental and applied biological sciences. Psychology; Humans; Miscellaneous; Molecular and cellular biology; Muscle contraction; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - metabolism; Myometrium - metabolism; Oxytocin; Radioligand Assay; Receptors, Vasopressin - metabolism; Smooth muscle cell, uterine; Smooth muscle cell, vascular; Tritium; Vasopressin; Vasopressins - metabolism
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/S0014-2999(99)00403-3

Several studies indicate that oxytocin and vasopressin receptors in the human uterus are heterogeneous. We have investigated whether oxytocin and vasopressin bind to separate receptors or one class of receptors in human uterine smooth muscle cells. [ 3 H ]d(CH 2) 5Tyr(Me)AVP, the vasopressin V 1A receptor selective radioligand, was used for comparison of vasopressin binding sites in human uterine and vascular smooth muscle cell membranes. Both membrane preparations exhibited one class of high-affinity binding sites with K d values of 6.44 and 0.47 nM, B max values of 166 and 34.8 fmol/mg protein for uterine and vascular smooth muscle cells, respectively. In vascular preparations, the selective vasopressin V 1A receptor antagonist, SR 49059 ((2 S) 1-[(2 R 3 S)-(5-chloro-3-(2-chlorophenyl)-1-(3,4-dimethoxybenzenesulfonyl)-3-hydroxy-2,3-dihydro-1 H-indole-2-carbonyl]-pyrrolidine-2-carboxamide), showed high affinity with K i value of 0.98 nM, confirming that these receptors belong to the vasopressin V 1A receptor subtype. On the contrary, in uterine preparations, binding of [ 3 H ]d(CH 2) 5Tyr(Me)AVP was more effectively displaced by oxytocin and the oxytocin receptor selective antagonist, L-371257, (1-{1-[4-[ N-Acetyl-4-piperidinyl)oxy]2-methoxybenzoyl]piperidin-4-yl}-4 H-3,1-benzoxazin-2(1 H)-one), than vasopressin and SR 49059, suggesting that binding may be due to cross-reaction with the oxytocin receptors. These results suggest that human uterine smooth muscle cells express only a high density of oxytocin receptors.