Cryopreservation affects endothelial and smooth muscle function of canine autogenous saphenous vein grafts

Cryopreserved veins used as arterial grafts may be affected by both rejection and the cryopreservation process. Experiments were designed to study changes in endothelial and smooth muscle function after cryopreservation but independent of rejection. One saphenous vein from each of eight dogs was cryopreserved for subsequent use as autografts. After 3 weeks one cryopreserved and one freshly harvested autogenous saphenous vein were implanted as bilateral femoral arterial interposition grafts. Platelet deposition was studied in vivo with indium 111-labeled platelets. At 4 weeks the autografts were removed, and the functional characteristics of the grafts were studied in organ chambers; and the ability of nerve terminals to uptake transmitter was studied with ³H-norepinephrine. Neither patency rates, blood flows, nor platelet deposition were significantly different between freshly harvested and cryopreserved grafts. Uptake of ³H-norepinephrine was significantly reduced in both grafts as compared to unoperated veins. The smooth muscle of the cryopreserved and fresh grafts contracted comparably to alpha-adrenergic agonists and endothelin. In cryopreserved grafts, the maximal tensions that developed to KCI, prostaglandin F_2α, and endothelin were greater when the endothelium was present compared to that developed by the smooth muscle alone. Calcium ionophore A23187 caused relaxations only in rings with endothelium; these were not significantly different between graft types. However, relaxations of the smooth muscle to nitric oxide were decreased in the cryopreserved grafts. These results suggest the following: (1) cryopreservation does not influence early patency rates, blood flows or platelet deposition in autogenous vein grafts; (2) functional nerve terminals are not present in fresh or cryopreserved autogenous vein grafts after 4 weeks; (3) an endothelium-derived relaxing factor is present in both fresh and cryopreserved autogenous vein grafts at 4 weeks. It remains to be determined as to whether the increased endothelial contractile responses and decreased relaxations of the smooth muscle of cryopreserved autogenous grafts would influence long-term patency of these grafts.