RESUMO
<p><b>OBJECTIVE</b>To compare the differences in nitric oxide (NO) release and endothelium-derived hyperpolarizing factor (EDHF)-mediated hyperpolarization between human radial artery (RA) and saphenous vein (SV) through direct measurement of NO and membrane potential.</p><p><b>METHODS</b>RA (n = 8), SV (n = 23), and surgical prepared SV (PV, n = 9, dilatation with normal saline solution at a pressure of 100 - 600 mmHg, 1 mmHg = 0.133 kPa) segments (5 mm long) taken from patients undergoing coronary artery bypass grafting were placed in an organ chamber. The NO-sensitive electrode and intracellular glass microelectrode was used to directly measure the NO release and the membrane potential changes in response to acetylcholine (ACh) and bradykinin (BK) before and after incubation with NG-nitro-L-arginine, indomethacin, and oxyhemoglobin.</p><p><b>RESULTS</b>The basal release of NO in RA [(11.9 ± 1.8) nmol/L] was significantly greater than that in SV [(9.9 ± 2.8) nmol/L, P = 0.041]. BK-induced NO release in RA was lower than that in SV [for BK 10(-7) mol/L: (25.8 ± 3.6) nmol/L vs. (43.7 ± 8.2) nmol/L, P = 0.006]. Both basal and ACh- or BK-induced NO release in PV were significantly reduced [basal release: PV (3.4 ± 1.4) nmol/L; P = 0.006 vs. RA; P = 0.002 vs. SV; stimulated release: for ACh 10(-5) mol/L: PV (4.8 ± 3.2) nmol/L; vs. RA (28.6 ± 7.9) nmol/L, P = 0.005; vs. SV (27.4 ± 3.7) nmol/L, P = 0.003; for BK 10(-7) mol/L: PV (7.0 ± 3.6) nmol/L; vs. RA (25.8 ± 3.6) nmol/L, P = 0.016; vs. SV (43.7 ± 8.2) nmol/L, P = 0.004]. EDHF-mediated hyperpolarization was greater in RA than that in SV [ACh 10(-5) mol/L: (-9.7 ± 1.9) mV vs. (-4.5 ± 1.1) mV, n = 17, P = 0.002].</p><p><b>CONCLUSIONS</b>RA is superior to SV in terms of NO basal release and EDHF-mediated endothelial function. Surgical preparation and pressure dilatation may severely impair the NO-mediated endothelial function of SV, which may contribute to the poor long-term patency of SV coronary graft.</p>