Abstract
Photodynamic Therapy (PDT) was shown to be effective for reduction atherosclelosis in a previous study. However its clinical use has been limited due to photodermatosis, a side effect of Photofrin. The purpose of this experiment was to suppress the occurrence of photodermatosis by local administration of minimal dose Photofrin. In the first experiment, atherosclerotic rabbits (mean body wight 3kg) were divided into two groups, the nomal dose group administered 5mg/kg (total dose 15mg) Photofrin intravenosly and the Dispatch group was given 15mg Photofrin through a Dispatch catheter, which can deliver drug to a limited area. After administration, they were examined by fluorescence microscopy and measured accumulation of Photofrin. Fluorescence microscopy revealed the presence of red fluorescence, indicating the presence of Photofrin. The stronger red fluorescence and the higher accumulation of Photofrin was observed in the Dispatch group. In the second experiment, Dispatch catheter was inserted through the femoral artery of rabbits and given 15mg of Photofrin to the atherosclerotic lesion on the aorta. After 10minutes, the lesions were then exposed to 200mW output YAG-OPO laser beam at 630nm for 10minutes from the intimal side of the aorta. The rabbits were then sacrificed 7days after irradiation. They were then examined by microscopy. PDT regions showed necrosis of intimal cells and disappearance of endothelial cells. The PDT and the non-PDT regions were expressed in terms of I/M ratio (intimal thickness/medial thickness). Results are the presented as mean±S. D. The I/M ratio of the PDT regions were 2.38±0.55, while that of the non-PDT regions were 4.09±0.49. The method of this administration via a Dispach catheter is useful for the clinical application of PDT.
