Altered responsiveness of saphenous vein grafts to norepinephrine and tyramine: relation to tissue catecholamine stores.

This study was designed to investigate early changes in reactivity in relation to the adrenergic innervation of venous grafts. Saphenous vein grafts were implanted into the carotid artery by the end-to-end technique in mongrel dogs. After 1 week, the grafts were harvested and dose-response curves to norepinephrine and tyramine were determined and compared with those of nongrafted saphenous veins and carotid arteries. Tissue norepinephrine levels of the blood vessels were measured by HPLC with electrochemical detection. Grafted vessels demonstrated an enhanced sensitivity to norepinephrine and a significant attenuation to tyramine. Additionally, grafted saphenous veins exhibited a significant depletion of norepinephrine content when compared to nongrafted veins. These differences suggest that denervation of the saphenous vein produces a supersensitivity to catecholamines that could account for enhanced vascular reactivity observed following implantation of saphenous vein grafts.