FUNCTIONAL AND HISTOLOGICAL DIFFERENCES IN AUTOGENOUS AND ALLOGENIC VEIN GRAFTS - 2 DIFFERENT VASCULOPATHIES

The long-term biological characteristics and the functional and morpho logical changes that occur in fresh allografts are poorly understood. This study tests the hypothesis that the development of intimal hyperp lasia and its associated functional changes are accelerated in an allo graft compared to an autograft due to the additional immunological sti muli. Common carotid vein bypass grafts were performed in 40 New Zeala nd White rabbits: 20 received their ipsilateral jugular veins (autolog ous) and 20 received the fresh contralateral jugular veins from the co ntrol. rabbit (allogenic), Electron microscopy was performed and intim al and medial dimensions were determined by videoplanimetry at 7, 14, and 28 days. Contraction and relaxation studies to a panel of agonists were also performed. The EC50's (agonist concentration which produces 50% of the maximal response) were calculated. Ail grafts remained pat ent. Allografts showed a 51% decrease in overall mean intimal thicknes s (41 +/- 3 mu m vs. 83 +/- 12 mu m; P < 0.01) and a 97% increase in o verall mean medial thickness (140 +/- 15 mu m vs. 71 +/- 3 mu m; P < 0 .01) compared to the autografts. The lumen of the allogenic vein graft s was equivalent to the autologous vein grafts. Overall mean total wal l thickness only increased by 17%, 181 mu m vs. 154 pm for allo- and a utografts, respectively, The EC50 for norepinephrine, histamine, and b radykinin were similar in the auto- and allografts, while the EC50 to serotonin was significantly less in the allografts than in the autogra fts. Neither the precontracted auto- or allografts relaxed to acetylch oline or serotonin (receptor mediated, endothelium dependent). The EC5 0 for calcium ionophore (nonreceptor mediated, endothelium dependent) was equivalent in the auto- and allografts. The EC50 for the sodium ni troprusside-induccd relaxation (endothelium independent) was significa ntly higher in the allograft than ill the autograft. This study demons trates that there are two different vasculopathies occurring in autogr afts and allografts: intimal hyperplasia is predominant in the autogra ft while an exaggerated medial response is predominant in the allograf t. Serotonin contractility and endothelial-independent relaxation are enhanced in the allograft compared to the autograft, (C) 1997 Academic Press.