Labetalol, nebivolol, and propranolol relax human radial artery used as coronary bypass graft.
OBJECTIVE
Beta-blockers are a heterogeneous class of agents that are used in the treatment of many cardiovascular diseases, especially hypertension and atherosclerosis, and that are commonly prescribed after cardiac surgery. In the present study, the aim is to investigate the vasorelaxant effects of some common beta-adrenoceptor blockers on the human radial artery in vitro, as well as their relaxation mechanisms.


METHODS
Radial artery rings sourced from human patients were mounted in an organ bath and tested for changes in isometric tension in relaxation response to labetalol, nebivolol, and propranolol in the presence and absence of NG-nitro-L-arginine methyl ester (3 × 10(-5) mol/L) and tetraethyl ammonium (3 × 10(-4) mol/L).


RESULTS
The labetalol (10(-8) to 10(-4) mol/L), nebivolol (10(-8) to 10(-4) mol/L), and propranolol (10(-8) to 10(-4) mol/L) induced concentration-dependent relaxations on the radial artery rings, which had been precontracted with phenylephrine (10(-6) mol/L). The relaxation response induced by labetalol in the isolated radial artery rings was significantly higher when compared with the nebivolol and propranolol samples (P < .05). NG-nitro-L-arginine methyl ester significantly reduced the relaxation of nebivolol (P < .05), and tetraethyl ammonium significantly reduced the relaxation of labetalol, nebivolol, and propranolol (P < .05).


CONCLUSIONS
We speculated that the relaxant effect of labetalol, nebivolol, and propranolol was due partly to the Ca(2+)-activated K(+) channels. In addition, the relaxation induced by nebivolol was largely related with nitric oxide release. Nebivolol, and partly propranolol, may provide significant therapeutic benefit, but labetalol can be a good alternative for coronary artery bypass grafting with radial artery use.
Department of Cardiovascular Surgery, Cumhuriyet University School of Medicine, Sivas, Turkey. Electronic address: ozgekorkmaz73@hotmail.com.
Ozge
O
Korkmaz
Department of Pharmacology, Cumhuriyet University School of Medicine, Sivas, Turkey.
Bülent
B
Saraç
Department of Cardiovascular Surgery, Cumhuriyet University School of Medicine, Sivas, Turkey.
Sabahattin
S
Göksel
Department of Pharmacology, Cumhuriyet University School of Medicine, Sivas, Turkey.
Sahin
S
Yildirim
Department of Cardiovascular Surgery, Cumhuriyet University School of Medicine, Sivas, Turkey.
Ocal
O
Berkan
Department of Pharmacology, Cumhuriyet University School of Medicine, Sivas, Turkey.
Ihsan
I
Bagcivan
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D001026:Coronary Artery Bypass / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007741:Labetalol / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D000068577:Nebivolol / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology*; D017534:Radial Artery / Q000187:drug effects* / Q000502:physiology / Q000601:surgery; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
D000319:Adrenergic beta-Antagonists; D004791:Enzyme Inhibitors; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D014665:Vasodilator Agents; D000068577:Nebivolol; D009569:Nitric Oxide; D011433:Propranolol; D019001:Nitric Oxide Synthase; D007741:Labetalol