Abstract

Objective: The aim of this study was to investigate in vitro effects of dopamine on internal thoracic artery (ITA) graft.

Material and Methods: Between December 2003- June 2005, 32 patients (2 women and 30 men, mean age; 59.26±8.34, range 37-75 years old) who were subjected to coronary artery bypass grafting (CABG) operation in our clinic were enrolled in this study. ITA remnants were suspended in an isolated organ bath. Constrictor or relaxant responses to dopamine were recorded isometrically.

Results: Dopamine in the concentration range of 10-9 M-10-7 M produced a mild relaxant effect on phenylephrine-precontracted ITA, and at higher concentrations than 10-7 M it produced a constrictor response. Ther relaxant effect of dopamine was partially antagonized by L-NAME (nitric oxide synthase inhibitor, 10-6 M), propranolol (10-6 M), and cis-α-flupenthixol (dopaminergic receptor antagonist, 10-6 M), but not by metoclopramide (D2-dopaminergic receptor antagonist). The constrictor effect of dopamine was partially antagonized by phentolamine, prazosin and, yohimbine.

Conclusion: It was concluded that, while dopamine produces a vasodilator response at the lower concentrations, it causes a constrictor effect on ITA at the higher concentrations. Both a β-adrenergic and a nitric oxide mediated mechanism (via D1-dopaminergic receptor) may play a role in the relaxant effect of dopamine on ITA at the lower concentrations. Constrictor response to dopamine at the higher concentrations on ITA may be produced by the activation of α1- and α2-adrenergic receptors.