Pharmacologic characterization of the internal mammary artery used in myocardial revascularization

The aim of this study concerned the pharmacological investigation of the isolated internal mammary artery. Spirally-cut vascular segments were obtained from patients undergoing myocardial revascularization and set up in isolated baths under isometrical tension. Reactivity of internal mammary artery preparations to stimulatory and inhibitory agents was evaluated. KCl (90 mM), noradrenaline (10-8)-10(-5) M) and serotonine (10(-9)-10(-5) M) induced a tonic contraction lasting for more than 60 min. Angiotensin II (10(-6)-10(-5) M) and dopamine (10)-8)-10(4) M) resulted virtually uneffective. The serotonine-induced contractions were strongly inhibited by ketanserin (10-9)-10(-6) M), a selective S2-blocker, and also by verapamil (10(-3)-10(-6) M) and nitroglycerin (10(-7)-10(-5) M). These data suggest that internal mammary artery is sensitive to different contractile agents, in particular serotonine activates muscular contractions through S2 receptors. The knowledge of such a mechanism may be of clinical relevance.