MOLECULAR MECHANISMS OF NOVEL ANTI-DIURETIC ANTAGONISTS - ANALYSIS OF THE EFFECTS ON VASOPRESSIN BINDING AND ADENYLATE-CYCLASE ACTIVATION IN ANIMAL AND HUMAN-KIDNEY

  • 1 January 1982
    • journal article
    • research article
    • Vol. 223  (1) , 50-54
Abstract
The molecular mechanisms of a potential new class of diuretic agents, vasopressin antagonists are described. Inhibition of the antidiuretic response to antidiuretic hormone (ADH) by the novel vasopressin analogs d(CH2)5 Tyr(Me)VAVP [[1-(.beta.-mercapto-.beta.,.beta.-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine,4-valine]arginine-vasopressin], d(CH2)5 Tyr(Et)VAVP [[1-(.beta.-mercapto-.beta.,.beta.-cyclopentamethylenepropionic acid), 2-(O-ethyl)tyrosine,4-valine]arginine-vasopressin], d(CH2)5 Tyr(Et)VDAVP [[1-(.beta.-mercapto-.beta.,.beta.-cyclopentamethylenepropionic acid), 2-(O-ethyl)tyrosine,4-valine, 8-D-arginine]vasopressin] and d(CH2)5D-TyrVAVP [[1-(.beta.-mercapto-.beta.,.beta.-cyclopentamethylenepropionic acid), 2-D-tyrosine,4-valine]arginine-vasopressin] was studied using medullary membranes of pig [dog and rat] kidney. These analogs were competitive inhibitors of vasopressin binding and adenylate cyclase activation by vasopressin with potencies that were 5- to 7-fold higher than those of d(CH2)5VDAVP [[1-(.beta.-mercapto-.beta.,.beta.-cyclopentamethylenepropionic acid), 4-valine, 8-D-arginine]vasopressin] (Kbind [binding constant] was 6.7 .times. 10-7 M; Ki [inhibition constant] was 2.3 .times. 10-7 M), an analog with no in vivo anti-ADH activity. The antagonists were judged to be selective for vasopressin receptors, because the activation of renal adenylate cyclase by .beta.-adrenergic agonists and prostaglandins E1, E2 and I2 was not affected by d(CH2)5D-TyrVAVP. Blockade of the vasopressin receptors with this analog did not impair the other components of the adenylate cyclase system, since basal enzyme activity and activity stimulated by guanyl-5''-yl imidodiphosphate and NaF were not diminished. d(CH2)5D-TyrVAVP was a potent inhibitor of vasopressin activation of adenylate cyclase in pig, rat and dog kidney, and also in human kidney (Ki was 1.9 .times. 10-8 M).

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