STRUCTURAL, BIOCHEMICAL AND FUNCTIONAL-EFFECTS OF DISTENDING PRESSUREIN THE HUMAN SAPHENOUS-VEIN - IMPLICATIONS FOR BYPASS-GRAFTING

Background Distension of the saphenous vein before and after coronary artery bypass grafting results in damage to mechanisms that regulate v ascular tone. We have investigated the relationship between the magnit ude of distending pressure and the degree of structural, biochemical a nd functional damage to the vessel wall, Methods Vessel segments that had been distended to either 100 or 300 mmHg were set up in isolated o rgan baths and the function of the smooth muscle and endothelial cells examined, All segments examined were then fixed for assessment of str uctural damage by scanning electron microscopy and for immunocytochemi cal localisation of endothelial nitric oxide synthase. Results Segment s of saphenous vein distended to 100 mmHg retained their responsivenes s to KCI (90 mmol/l) and phenylephrine (10(-6) mol/l), but those press urised to 300 mmHg had significantly reduced responses to both agents. There was also a significant reduction in response to the endothelium -dependent dilators, acetylcholine (10(-10)-10(-6) mol/l) and bradykin in (10-10-10-6 mol/l) in those segments distended to 300 mmHg. Quantit ative studies of structural endothelial damage showed a significant lo ss of endothelium at 300 mmHg distension pressure. Remaining endotheli al cells retained strong positive staining for endothelial nitric oxid e synthase. By electron microscopic examination, those vessels distend ed to 100 mmHg showed lifting and rounding of individual cells, wherea s segments distended to 300 mmHg revealed major areas of denuded endot helium, Conclusions Distension of saphenous veins to pressures equival ent to those in the systemic circulation result in structural and bioc hemical changes in the endothelium that are not paralleled by immediat e functional vasomotor changes. Coronary Artery Dis 9:143-151 (C) 1998 Lippincott-Raven Publishers.