Photodynamic therapy (PDT) was shown to be effective for reduction of atherosclelosis in a previous study. We assessed PDT effect quantitatively using a diffuse irradiating fiber after hematoporphyrin derivative (HpD) administration. In the first experiment, atherosclerotic rabbits were given 5mg/kg HpD the dosage used clinically for lung cancer PDT. A 0.8mm-diameter plastic fiver was inserted through the femoral artery and a 200mW Argon-Dye laser beam of 630nm was delivered for 10 minutes. They were examined histologically immediately, 1 week, 2 weeks after PDT. The immediately after group shown damaged intimal cells and disappearance of endothelial cells. 1-week and 2-week groups showed necrosis of intimal cells, disappearance of the intima and exposure of the internal elastic lamina. In addition, HpD accumulation into the atherosclerotic intima was examined. Atherosclerotic rabbits were divided into three groups : the normal dose group administered 5mg/kg Hpd intravenously, the 1/3 dose group administered 1.7mg/kg Hpd intravenously and the Dispatch group (Dispatch catheter can deliver drug to a limited area) was given 1/3 dose (1.7mg/kg). 24 hours after (the normal dose group and the 1/3 dose group) and immediately after (the Dispatch group) administration, they were examined by fluorescence microscopy and a fluorescence analysis system. The highest peak at 630nm of HpD was observed in the Dispatch group. The ratio of intimal thickness and medial thickness in irradiated regions was significantly reduced compared with non-irradiated regions. The internal area of the aorta in irradiateed regions was increased significantly compared with non-irradiated regions. These results suggest that PDT using a new fiber is effective for human coronary artery. The method of administration using a Dispatch catheter may be usefull for PDT.
