Pharmacological characterization of the human vasopressin receptor subtypes stably expressed in Chinese hamster ovary cells

Abstract

Three subtypes of human (h) arginine vasopressin (AVP) receptors, hV 1A , hV 1B and hV 2 , were stably expressed in Chinese hamster ovary (CHO) cells and characterized by [ 3 H]‐AVP binding studies. In addition, the coupling of the expressed receptor protein to a variety of signal transduction pathways was investigated. Scatchard analysis of saturation isotherms for the specific binding of [ 3 H]‐AVP to membranes, prepared from CHO cells transfected with hV 1A , hV 1B and hV 2 receptors, yielded an apparent equilibrium dissociation constant ( K d ) of 0.39, 0.25 and 1.21 n m and a maximum receptor density ( B max ) of 1580 fmol mg −1 protein, 5230 fmol mg −1 protein and 7020 fmol mg −1 protein, respectively. Hill coefficients did not differ significantly from unity, suggesting binding to homogenous, non‐interacting receptor populations. Pharmacological characterization of the transfected human AVP receptors was undertaken by measuring the relative ability of nonpeptide AVP receptor antagonists, YM087, OPC‐21268, OPC‐31260, SR 49059 and SR 121463A, to inhibit binding of [ 3 H]‐AVP. At hV 1A receptors, the relative order of potency was SR49059>YM087>OPC‐31260>SR 121463A>>OPC‐21268 and at hV 2 receptors, YM087=SR 121463A>OPC‐31260>SR 49059>>OPC‐21268. In contrast, the relative order of potency, at hV 1B receptors, was SR 49059>>SR 121463A=YM087=OPC‐31260=OPC‐21268. In CHO cells expressing either hV 1A or hV 1B receptors, AVP caused a concentration‐dependent increase in intracellular Ca 2+ concentration ([Ca 2+ ] i ) with an EC 50 value of 1.13 n m and 0.90 n m , respectively. In contrast, stimulation of CHO cells expressing hV 2 receptors resulted in an accumulation of cyclic AMP with an EC 50 value of 2.22 n m . The potency order of antagonists in inhibiting AVP‐induced [Ca 2+ ] i or cyclic AMP response was similar to that observed in radioligand binding assays. In conclusion, we have characterized the pharmacology of human cloned V 1A , V 1B and V 2 receptors and used these to determine the affinity, selectivity and potency of nonpeptide AVP receptor antagonists. Thus they may prove to be a valuable tool in further examination of the physiological and pathophysiological roles of AVP. British Journal of Pharmacology (1998) 125 , 1463–1470; doi: 10.1038/sj.bjp.0702220

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