Pharmacological comparison of human internal mammary artery and radial artery in terms of conduits for revascularization
Internal mammary arteries (IMA) are routinely used for coronary artery bypass grafting (CABG). but can exhibit impairment of endothelium-dependent vascular relaxation. The use of radial artery (RA) grafts for CABG has been recently reintroduced. The long-term patency of these grafts may depend on the ability of these vessels to produce endothelium-derived nitric oxide (NO). We therefore sought to determine if the RA exhibits better endothelial function compared with 1MA harvested from the same patient. Using the organ bath technique, vessels were preconstricted with the thromboxane A 2 analogue (U46619) and exposed to increasing concentrations of either acetylcholine (ACh), calcium ionophore A23187 (A23187), or nitroglycerin (NTG). We prepared the rubbed RA for comparison of between RA with and without endothelium on response to ACh relaxation. KCl and U46619 constricted RA (11.3 ± 4.9 g and 16.0 ± 4.3 g respectively) more than 1MA (2.4 ± 1.4 g and 4.5 ± 1.7 respectively). Both RA and IMA relaxed 100% of the preconstricted tension to NTG. ACh induced less relaxation in the 1MA (28 ± 24 %) when compared with the RA (49 ± 16%) (p<0.05). A23187 demonstrated relaxation in both the RA (86 ± 14%) and IMA (76 ± 18%), but there was no statistical difference. RA without endothelium showed same response to ACh as IMAs. Compared with the IMA, the RA has better ACh induced endothelium-dependent relaxation. This pathway mainly involves NO production which also inhibits the atherosclerotic process. Therefore, the RA may provide longer term graft patency than IMA.
Koji, Y; Szlam, F; Levy, JH; Tetsuji, M
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