Vein Contraction And Smooth Muscle Cell Extensions As Causes Of Endothelial Sloughing During Graft Preparation

In this study light, transmission and scanning electron microscopy were used to investigate the effects of various methods of vein graft preparation on endothelial and smooth muscle cells (SMC) of the dog cephalic vein. After removal, veins were stored in one of three heparinized solutions at 10°C for 5 minutes or 1 hour: autologous blood, Plasma-Lyte or Plasma-Lyte with 0.6 mg/ml Papaverine added. The vein wall proved very sensitive to dissection, manipulation and introduction of fixative and reacted to such stimuli with a severe contraction which not only diminished the luminal diameter, but also resulted in formation of medial SMC cytoplasmic extensions and protrusion of the endothelial cells into the lumen. The SMC cytoplasmic extensions were particularly frequent in the immediate subendothelial area and seem to play a role in lifting up, separating or desquamating the endothelial cells. Such findings also are relevant to the chronic effects of arterial spasm. Among the stored veins, those soaked in blood showed the greatest vessel wall contraction and endothelial cell loss. Veins soaked in Plasma-Lyte-Papaverine had the most relaxed and normal appearance and the least endothelial cell loss. If the Papaverine treated veins were subsequently subjected to brief distension at 100 mmHg, however, large gaps appeared between the endothelial lining cells. The results suggest that Papaverine treatment greatly reduces vein graft endothelial cell loss due to contraction, but Papaverine-induced relaxation should be reversed before the graft is subjected to arterial pressure.