Pharmacological characterization of YM087, a potent, nonpeptide human vasopressin V1A and V2 receptor antagonist

Abstract

The effects of YM087 (4’-[(2-methyl-1,4,5,6-tetrahydroimidazo[4,5-d][1]benzazepin-6-yl)-carbonyl]-2-phenylbenzanilide monohydrochloride), a novel nonpeptide vasopressin (AVP) receptor antagonist, on [³H]AVP binding to human AVP receptors (V_1A, V_1B and V₂) cloned and transiently expressed in COS-1 cells generated from monkey renal tissue were studied. Scatchard analysis of saturation isotherms for the specific binding of [³H]AVP to membranes, prepared from COS-1 cells transfected with human V_1A, V_1B and V₂ receptors, yielded an apparent equilibrium dissociation constant (K _d) of 0.67nM, 0.28nM and 2.14nM and a maximum receptor density (B _max) of 2180fmol/mg protein, 369fmol/mg protein and 2660fmol/mg protein, respectively. YM087 showed high affinity for AVP V_1A and V₂ receptors with K _i values of 6.3 and 1.1nM, respectively, but had no effect on [³H]AVP binding to AVP V_1B receptors.

In COS-1 cells expressing either AVP V_1A or V_1B receptors, AVP caused a concentration-dependent increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i). YM087 inhibited the AVP-induced increase in [Ca²⁺]_i in COS-1 cells expressing AVP V_1A receptors in a concentration-dependent manner with an IC₅₀ value of 14.3nM, but did not influence this increase in AVP V_1B-receptor expressing cells. In contrast, stimulation of COS-1 cells expressing AVP V₂ receptors resulted in an accumulation of cAMP. YM087 inhibited AVP-induced cAMP production in COS-1 cells expressing AVP V₂ receptors in a concentration-dependent manner with an IC₅₀ value of 1.95nM. In all assays used, YM087 was devoid of any agonistic activity.

These results suggest that YM087 is a potent nonpeptide dual human AVP V_1A and V₂ receptor antagonist, and that YM087 will be a powerful tool in investigation of the physiological and pathophysiological roles of AVP.