title: Retention and photodynamic effects of haematoporphyrin derivative in cells after prolonged cultivation in the presence of porphyrin.
abstract: Photoradiation therapy of cancer in the presence of haematoporphyrin derivative is based on a retention of porphyrin in malignant tissue. After long term incubation of NHIK 3025 cells in the presence of 25 microgram ml-1 haematoporphyrin derivative, one fraction is easily removed from the cells by washing with a serum-rich medium. Another fraction remains bound to the cells for a prolonged time. The former does not contribute to the photosensitivity of the cells while the latter, the tightly-bound component, results in a photosensitivity proportional to the cellular contents of porphyrin. Transformed cells are shown to be slightly more sensitive and to retain 25-50% more haematoporphyrin derivative than non-transformed cells. Cytological effects of light absorbed by the tightly-bound component have been studied. The growth of treated cells is similar to that of control cells after a dose-dependent post irradiation lag period. A relatively slow leakage of lactate dehydrogenase (LDH) out of the cells takes place after treatment. The treatment induces a significant increase in the frequency of sister chromatid exchanges (SCE). We conclude that photoactivation of the tightly-bound fraction of haematoporphyrin derivative induces less damage to the outer cell membrane and probably more intracellular damage than irradiation of cells after a short period in contact with the derivative.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000528:radiation effects; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D002471:Cell Transformation, Neoplastic / Q000378:metabolism; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D017324:Hematoporphyrin Derivative; D006415:Hematoporphyrins / Q000378:metabolism*; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008027:Light; D051379:Mice; D011838:Radiation-Sensitizing Agents / Q000378:metabolism*; D012854:Sister Chromatid Exchange / Q000528:radiation effects; D013997:Time Factors
chemical_list: D006415:Hematoporphyrins; D011838:Radiation-Sensitizing Agents; D017324:Hematoporphyrin Derivative; D007770:L-Lactate Dehydrogenase