Comparative effects of tolazoline and nitroprusside on human isolated radial artery.
BACKGROUND
The radial artery is increasingly being used in coronary revascularization as an alternative conduit to a saphenous vein graft. Its perfect endothelial capacity provides a high patency rate comparable with the internal mammary artery (IMA). However, its spastic characteristics cause difficulties during its intraoperative preparation and may lead to early postoperative graft failure. Thus, treatment and/or prevention of radial artery spasm with an effective vasodilator agent is essential for its longevity. Endogenous vasoconstrictors, including noradrenaline, endothelin-1, and thromboxane A2, are likely to play a role in the pathogenesis of graft spasm. In the present study, we evaluated the vasorelaxant effect of tolazoline, a nonselective alpha-adrenoceptor blocker, against the contractions induced by various spasmogenic agents in an isolated human radial artery.


METHODS
Tolazoline (10(-9)-10(-4) M) or sodium nitroprusside (SNP, 10(-9)-10(-4) M) were cumulatively applied on radial artery rings precontracted submaximally with noradrenaline, endothelin-1, thromboxane analogue, U46619, or potassium chloride. In addition, some rings were pretreated with tolazoline (4 x 10(-6) M) for 30 minutes and the contractile response curve to noradrenaline was assessed in its presence.


RESULTS
Tolazoline effectively reversed noradrenaline-induced contractions in the radial artery, whereas it failed to produce remarkable relaxations on rings contracted with other spasmogenic agents, while SNP overcame the contractions induced by all spasmogens to a similar extent. In addition, brief pretreatment of radial artery rings with tolazoline significantly inhibited the contractions to noradrenaline.


CONCLUSIONS
Tolazoline is not as broadly effective as SNP against all spasmogens investigated; however, it may be effective in counteracting alpha-adrenoceptor-mediated vasospasm in human radial arteries.
Teskin
Onder
O
Department of Cardiovascular Surgery, Siyami Ersek Thoracic and Cardiovascular Surgery Education and Research Hospital, Istanbul, Turkey.
Uydeş-Dogan
B Sönmez
BS
Enç
Yavuz
Y
Alp
F Ilkay
FI
Kaleli
Deniz
D
Keser
Süheyla
S
Iyigün
Taner
T
Bilgen
Fuat
F
Dagsali
Sabri
S
Ozdemir
Osman
O
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D004353:Drug Evaluation, Preclinical; D019332:Endothelin-1 / Q000494:pharmacology; D006801:Humans; D009599:Nitroprusside / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D017534:Radial Artery / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology; D014043:Tolazoline / Q000494:pharmacology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*
D019332:Endothelin-1; D011942:Receptors, Adrenergic, alpha; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D011189:Potassium Chloride; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D014043:Tolazoline; D009638:Norepinephrine