The present study was designed to evaluate the association between chronic kidney disease and the endothelial function of internal thoracic artery (ITA) grafts in patients undergoing coronary bypass surgery. An isometric tension study was performed in ITA strips obtained during surgery. Concentration-response curves for acetylcholine (ACh) and sodium nitroprusside were constructed in ITA strips partially precontracted with phenylephrine under the inhibition of cyclooxygenase. The integrity of the endothelium was verified histologically by en-face staining of the luminal surface with the use of silver nitrate solution.Results:
In endothelium-intact ITA strips, ACh produced a concentration-dependent relaxation in patients with glomerular filtration rate (GFR, mL/min/1.73 m2) > 60. A concentration-dependent relaxation response also was observed in patients with GFR 30 to 60, but it was reduced significantly compared with those with GFR > 60. In both groups, removal of endothelium or treatment with nitric oxide (NO) synthase inhibitors almost abolished the ACh-induced relaxation. On the other hand, in patients with GFR < 30, mild contraction rather than relaxation was induced at a high concentration of ACh, which was modified neither by treatment with NO synthase inhibitors nor by removal of the endothelium. Vasodilator responses to sodium nitroprusside were comparable among the 3 groups. The relaxation of endothelium-intact strips to a peak ACh concentration correlated positively with GFR. This relationship held true in a multiple linear regression model, and interaction terms between GFR and other risk factors were not statistically significant.Conclusions:
Endothelial function of ITA grafts to release NO is impaired at the time of surgery in patients with chronic kidney disease.