PHOTODYNAMIC EFFICACY OF NATURALLY-OCCURRING PORPHYRINS IN ENDOTHELIAL-CELLS IN-VITRO AND MICROVASCULATURE IN-VIVO

Photodynamic therapy (PDT) has been described in terms of cellular and vascular effects. The precise mechanisms of cellular and vascular dam age are still unknown. In this study, the photodynamic inactivation of endothelial cells in vitro and damage to the microvasculature in vivo by naturally occurring porphyrins (uroporphyrin III (UP), coproporphy rin III (CP) and protoporphyrin IX (PP)) were investigated. The chick chorioallantoic membrane model (CAM model) was used, which is convenie nt for the study of damage to the microcirculation induced by PDT. The hydrophilic porphyrins UP and CP exhibited low cytotoxicity towards e ndothelial cells. Only small amounts of UP and CP were taken up, resul ting in weak inactivation after irradiation. In contrast, the more lip ophilic PP showed a marked cytotoxicity. Considerable amounts of PP we re accumulated in the cells, leading to pronounced inactivation after light exposure. For the three porphyrins, damage to the microvasculatu re was observed. The damage caused by the hydrophilic porphyrins UP an d CP was strongly dependent on the drug and light dose. For vascular i njury, the efficacy was graded as UP < CP < PP. (C) Elsevier Science S .A.