Today most cardiovascular surgeons prefer artery grafts to vein grafts, because of their better long term patency. Recently we reported monocyte/macrophage infiltration and the development of intimal hyperplasia (IH) is different in rat epigastric vein to common femoral artery interposition graft, from common femoral artery transection and re-anastomosis. Tumor Necrosis Factor-α (TNF-α) has been well known as one of the growth factors produced from activated macrophages. We hypothesize TNF-α mRNA expression is different in vein graft compared to femoral artery re-anastomosis. Lewis rats underwent either epigastric vein to common femoral artery interposition grafts (VG: n = 25) or common femoral artery transection and re-anastomoses (FA: = 4 24). Vessels were harvested at 0 hour, 1 hour, 3 hours, 1 day, 4 days, 1 week and 2 weeks. To compare the development of IH, vessel wall areas were calculated and described as the intimal area/total area (Ri). TNF-α mRNA expression was examined by using reverse transcription-polymerase chain reaction, and was compared with S-26 mRNA expression on computerized densitometry. The TNF-α/S-26 mRNA expression ratio was increased in VG compared to FA re-anastomosis, especially at 1 week (p &lt
0.01). These results suggest that the mechanism of IH is different between vein graft and artery graft.