title: Singlet oxygen intermediacy in the photodynamic action of membrane-bound hematoporphyrin derivative.
abstract: The cell-damaging photochemistry of hematoporphyrin derivative (HPD) has been investigated using isolated erythrocyte membranes as a test system. Irradiation of membranes in the presence of the tumor-localizing fraction of HPD resulted in formation of singlet molecular oxygen (1O2) as measured by the phosphorescence at 1268 nm. The authentic product of 1O2 attack on cholesterol, 3 beta-hydroxy-5 alpha-cholest-6-ene-5-hydroperoxide, was identified in this system. Relatively insignificant amounts of free radical-derived hydroperoxides were detected. These results suggest that 1O2 plays a major role in the HPD-sensitized photokilling of tumor cells in vivo.
mesh_terms: D002784:Cholesterol / Q000031:analogs & derivatives / Q000032:analysis; D002855:Chromatography, Thin Layer; D004910:Erythrocyte Membrane / Q000378:metabolism* / Q000528:radiation effects; D017324:Hematoporphyrin Derivative; D006415:Hematoporphyrins / Q000378:metabolism*; D006801:Humans; D008163:Luminescent Measurements; D010100:Oxygen; D010777:Photochemistry; D011838:Radiation-Sensitizing Agents / Q000378:metabolism*
chemical_list: D006415:Hematoporphyrins; D011838:Radiation-Sensitizing Agents; D017324:Hematoporphyrin Derivative; C002843:cholesterol hydroperoxide; D002784:Cholesterol; D010100:Oxygen