Differences in Angiotensin Convertase Enzyme (ACE) Activity and Expression May Contribute to Shorter Event Free Period After Coronary Artery Bypass Graft Surgery

SUMMARY Aims: The goal of this study was to investigate the importance of the vascular angiotensin convertase enzyme (ACE) in coronary artery bypass graft surgery (CABG) patients. Methods: Vascular tissue (distal saphenous vein [n= 163] and/or radial artery [n= 120] segments) and blood samples were collected from CABG patients (n= 81). We studied (i) the potency of angiotensin I (AngI) and angiotensin II (AngII) to evoke vascular contractions; (ii) vascular and plasma ACE concentrations; and (iii) ACE genotype of the patients enrolled. Results: The ratio of the potencies (EC50) of AngII and AngI was significantly lower in radial artery compared to the saphenous vein (0.17 ± 0.03 nM and 0.51 ± 0.14 nM, respectively, P= 0.003), suggesting a 3-fold more effective AngI conversion in saphenous vein samples. Angiotensin constrictions were inhibited with telmisartan and captopril in both saphenous veins and radial arteries. Vascular ACE expression was significantly higher in saphenous vein compared to radial artery (9.7 ± 1.0 ng/mg and 5.3 ± 0.7 ng/mg, respectively, P= 0.01). Serum but no tissue ACE concentration was determined by ACE insertion/deletion polymorphism. Accordingly, no relation was found between serum and tissue ACE expression. Conclusion: ACE-inhibitor therapy targeting tissue located ACE may be beneficial to patients with saphenous vein grafts after CABG surgery.