Anti-Hypertension Effect of Vanylidilol: A Phenylaldehyde α/β-Adrenoceptor Blocker with Endothelium-Dependent and K[sup +] Channels Opening-Associated Vasorelaxant Activities.

The antihypertensive effect of vanylidilol, a new α/β-adrenoceptor antagonist with endothelium-dependent and K[sup +] -channel-opening activities, was investigated in normotensive and hypertensive Wistar rats. Vanylidilol competitively antagonized (–)isoproterenol-induced positive chronotropic effects, inotropic effects, and tracheal relaxation effects in isolated rat right atria, left atria, and guinea pig tracheal strips in a concentration-dependent manner. Vanylidilol’s apparent pA[sub 2] values were 6.36 ± 0.08 (right atria), 6.41 ± 0.07 (left atria), and 6.31 ± 0.06 (trachea). Vanylidilol also produced a competitive antagonism of phenylephrine-induced contraction in the isolated rat aorta with pA[sub 2] values of 6.79 ± 0.18. In the radioligand binding assay, vanylidilol inhibited [[sup 3] H]CGP-12177 binding to rat ventricle and lung tissues and [[sup 3] H]prazosin binding to brain membranes with Ki values of 535.17, 2,066.69, and 431.11, respectively. In isolated rat thoracic aorta, vanylidilol’s vasorelaxant effects on phenylephrine (10 μmol/l)-induced contractions were attenuated by removing endothelium and by the presence of L -N[sup G] -nitro arginine methyl ester (L-NAME; 100 μmol/l), methylene blue (10 μmol/l), 1H-[1,2,4]oxadiazolol[4,3,-a] quinoxalin-1-one (ODQ; 10 μmol/l), tetraethylammonium (10 mmol/l), glibenclamide (1 μmol/l), apamin (1 μmol/l), and charybdotoxin (0.1 μmol/l). In addition, vanylidilol, in an equally antagonistic activity, inhibited phenylephrine-induced phasic and tonic contractions. Intravenous vanylidilol further reduced mean blood pressure in pentobarbital-anesthetized normotensive Wistar rats in a dose-dependent manner. The oral administration of vanylidilol to conscious spontaneously hypertensive rats had a long-lasting hypotensive effect on the heart rate and decreased it in a dose-dependent manner. Furthermore, vanylidilol’s vasodilator effect can be attributed in part to the release of NO or NO-related substance from vascular endothelium, while the endothelium-independent mechanism involved in vanylidilol’s relaxation is probably linked to the activation of the K[sup +] channels and the α-adrenoceptor blocking activity in these vessels. Copyright © 2004 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]