Morphological and functional study of free arterial grafts.

Morphological and functional changes of free arterial grafts in dogs were studied for 3 weeks after implantation and the changes were compared to those in implanted free vein grafts. In the arterial grafts, endothelial cells with abundant pinocytotic vesicles and some cytoplasmic folds were observed by transmission and scanning electron microscope and cell detachment was seen only at the site of anastomosis, while most cells were detached in the vein grafts. The site of mechanical damage in the arterial grafts was covered by regenerated endothelial cells which showed similar morphological findings to the normal arterial endothelial cells. In contrast, regenerated cells in the vein grafts started to cover the denuded area 7 days after the implantation and had completely covered it by 3 weeks. Prostacyclin was produced more abundantly in arterial grafts than in vein grafts at any phase after implantation. The level of prostacyclin production was between 30 and 40 pg/mg in any phase after implantation of free arterial grafts, while in vein grafts the level was 2.5 pg/mg at the day of implantation and increased to 13.6 pg/mg at 21 days. This study showed that the endothelial cells were well preserved and the level of prostacyclin production was high in the arterial grafts, and thus the grafts seemed to show potent anti-thrombogenicity after implantation. Although late changes in arterial and vein grafts were not investigated in this experimental protocol, these results may suggest that the arterial graft is superior to the vein graft even in the early period after its implantation as a free graft.