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Radiation therapy inhibits restenosis after coronary intervention but appears to exert long-term inhibition of endothelial recovery. Also, to avoid geographic miss, normal artery adjacent to the intervention site is irradiated during brachytherapy procedures. The effect of vascular brachytherapy on normal coronaries, mimicking such segments, has not been studied. We investigated ex vivo vasomotor function at long-term follow-up after endovascular brachytherapy, and correlated functional responses to morphology and eNOS expression. Vascular responses of pig coronaries to endothelium-dependent and independent vasoactive agents 3 mo after active irradiation (RAD; n= 12; 20Gy β), sham (S; n= 8; catheter with inactive wire), and in native controls (C; n= 8) were examined. Endothelial morphology was studied by scanning electron microscopy (SEM), and eNOS immunohistochemistry was …