LONG-TERM STRUCTURAL ALTERATIONS TO ENDOTHELIAL-CELLS IN VEIN-TO-ARTERY GRAFTS - A QUANTITATIVE ELECTRON-MICROSCOPIC STUDY

The intracellular structure of endothelium lining vein-to-artery graft s in rats was analysed, using transmission electron microscopy and mor phometry, to determine the ultrastructural adaptations of endothelial cells in this altered vascular environment. Autogenous 4-mm sections o f iliolumbar veins were inserted microsurgically into the left common iliac arteries of 16 male Wistar rats. At 3, 6, 26 and 52 weeks the cy toplasmic-vesicular, mitochondrial and rough endoplasmic reticular con tents of endothelial cells lining the grafts, the opposite iliac arter ies and the remaining ilio-lumbar veins were analysed morphometrically . There was a significant increase in the amount of all these cytoplas mic structures in endothelial cells at 3, 6 and 26 weeks; at 52 weeks there was also a significant increase in the volumes of mitochondria a nd cytoplasmic vesicles, but not in rough endoplasmic reticulum. It wa s concluded that the ultrastructure of endothelial cells lining these grafts is changed chronically after graft insertion, and we propose th at this may be attributable to altered haemodynamic stresses within th e graft.