Segments of radial artery and internal mammary artery were obtained from patients undergoing coronary artery bypass grafts, cut into two segments (≈5 mm in length) and placed in two organ chambers for isometric tension recording. Atorvastatin or pravastatin was added to one chamber and after a 2h stabilization period, contractions to a plateau were elicited with 70 mM KCl. Then the rings were precontracted with 10-7 M noradrenaline and cumulative relaxation curves to 10-9 to 10-4 M acetylcholine and sodium nitroprusside (10-8 to 10-4 M) were then performed. Contraction to KCl was significantly higher in the radial artery than in the internal mammary and the opposite was obtained with NA-induced contractions. In both vessels, statins did not modify the KCl contraction. Atorvastatin reduced the response to NA in the radial artery. The radial artery and the internal mammary artery precontracted with NA, relaxed dose-dependently in response to ACh. The relaxation was significantly higher in the radial than in the internal mammary, both with and without pretreatment with atorvastatin or pravastatin. These findings demonstrate a lack of effect of acute treatment with atorvastatin or pravastatin on the modulation of vascular tone in segments of human radial and internal mammary artery as measured by endothelium-dependent relaxation induced by ACh.
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