Acutely sodded expanded polytetrafluoroethylene grafts produce only prostacyclin: A qualitative difference from saphenous veins

Select subsets of patients require prosthetic graft material fur revascular ization. Although arterial prosthetic grafts of large caliber perform accep tably, grafts of <6 mm exhibit a high attrition rate. Microvessel endotheli al sodding, a method resulting in the lining of prosthetic grafts with auto logous endothelium, improves graft patency; however, aggressive antiplatele t therapy is still required, because terminating an antiplatelet regimen ac celerates graft attrition. The present investigation was designed to addres s the acute production of vasoactive substances in microvessel endothelial cell sodded expanded polytetrafluoroethylene (ePTFE) grafts in an attempt t o delineate a possible mechanism behind the continued requirement for antip latelet therapy. Equal lengths of acutely sodded ePTFE grafts (canine falci form ligament source) and saphenous veins (SV) (canine source) were evaluat ed by superfusion bioassay. Basal secretion from ePTFE grafts relaxed the b iodetector ring 1 +/- 3%, whereas SV relaxed the ring 10 +/- 3% (p < 0.05, ePTFE vs. SV). Relaxation with acetylcholine stimulation was 49 +/- 7% in g rafts and 50 +/- 10% in veins (p = NS). Calcium ionophore stimulation produ ced relaxation of 37 +/- 9% from ePTFE grafts and 100 +/- 23% from SV (p < 0.05). Indomethacin added to perfusate reduced relaxations from sodded ePTF E grafts to 20.2 +/- 9.2% with acetylcholine stimulation and 12.5 +/- 4.3% with calcium ionophore (p < 0.05 vs. control): addition of N-G-monomethyl-L -arginine (L-NMMA) had no effect on the release of vasoactive substances fr om ePTFE grafts. In contrast, relaxations of effluent from SV stimulated by acetylcholine and calcium ionophore were significantly attenuated with ind omethacin and L-NMMA (p < 0.05 vs. control). Scanning electron microscopy d emonstrated confluent endothelium in SV and a nonconfluent endothelial cell layer in grafts. Acutely sodded ePTFE grafts produce vasoactive substances that quantitatively and qualitatively differ from those produced by canine SV. The ePTFE grafts produce mainly prostanoids, whereas SV produce both n itric oxide and prostanoids. The endothelial cell isolation procedure and a bsence of immediate graft luminal confluence may contribute to the observed differences.