Nebivolol: endothelium-mediated vasodilating effect.

Area of Science:

• Pharmacology
• Cardiovascular Physiology
• Endothelial Function

Background:

• Nebivolol is a highly beta1-selective adrenoceptor antagonist with unique vasodilating properties.
• Unlike classical beta-blockers, nebivolol's vasodilatory mechanism, distinct from alpha-adrenergic antagonism, was not fully elucidated.
• Endothelial nitric oxide (NO) pathway involvement was suspected due to observed relaxation in canine arteries.

Purpose of the Study:

• To investigate the mechanism of nebivolol-induced vasodilation, specifically the role of the L-arginine/NO pathway.
• To compare nebivolol's vasodilatory effects with atenolol in human vasculature.
• To assess nebivolol's vasodilatory effects in patients with essential hypertension.

Main Methods:

• Forearm blood flow (FBF) was measured using venous occlusion plethysmography in healthy men and patients with essential hypertension.
• Infusions of nebivolol, its enantiomers, atenolol, carbachol, nitroprusside, and N(G)-monomethyl-L-arginine (LNMMA) were administered via brachial artery.
• The effect of LNMMA (a nitric oxide synthase inhibitor) and L-arginine on nebivolol-induced vasodilation was assessed.

Main Results:

• Nebivolol significantly increased FBF in healthy subjects and hypertensive patients, an effect absent with equimolar atenolol.
• Nebivolol-induced vasodilation was antagonized by LNMMA, indicating dependence on the L-arginine/NO pathway.
• L-arginine abolished the LNMMA antagonism, confirming the pathway's role; nebivolol's enantiomers showed similar vasodilatory effects.

Conclusions:

• Nebivolol induces vasodilation in human resistance vessels through the endothelial L-arginine/NO pathway.
• This mechanism differs from atenolol and contributes to nebivolol's unique hemodynamic profile.
• Chronic nebivolol treatment may offer benefits in hypertension and heart failure by reducing cardiac preload and afterload.