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Surgical preparation abolishes endothelium-derived hyperpolarizing factor-mediated hyperpolarization in the human
1Department of Surgery, University of Hong Kong, Grantham Hospital, Aberdeen, Hong Kong.
Background:
The impairment of the synthesis and release of endothelium-derived relaxing factors may be related to the high incidence of atherosclerosis and occlusion in saphenous vein grafts. This study focused on the effect of surgical preparation on one of the endothelium-derived relaxing factors, endothelium-derived hyperpolarizing factor, in the human saphenous vein.
Methods:
Human saphenous vein segments taken from patients undergoing coronary bypass were placed in an organ bath. A glass microelectrode was inserted into a smooth muscle cell. The membrane potential in response to acetylcholine (-9 to -5 log M) was measured in normal or surgically prepared saphenous vein with presence or absence of NG-nitro-L-arginine (300 mumol/L) and indomethacin (7 mumol/L).
Results:
The resting membrane potential was -71.28 +/- 1.91 mV (n = 7) with intact endothelium and -65.5 +/- 2.92 mV (n = 6, p > 0.05) without endothelium. Acetylcholine hyperpolarized membrane potential with intact endothelium (-90.57 +/- 1.48 mV, n = 7, p < 0.001), but not without endothelium (-69.67 +/- 2.93 mV, n = 6, p > 0.05). In the surgically prepared saphenous vein, acetylcholine did not hyperpolarize membrane potential (-71.83 +/- 3.84 mV versus the resting membrane potential of -69.50 +/- 3.53 mV, n = 6, p > 0.05).
Conclusions:
The endothelium-derived hyperpolarizing factor plays a role in the human saphenous vein. The surgical preparation abolishes the endothelium-derived hyperpolarizing factor-mediated hyperpolarization in the saphenous vein. This study provides evidence of functional changes of endothelium by traditional surgical preparation from another point of view, and it may be related to the high incidence of occlusion in saphenous vein grafts.