LIGHT INDUCED RELOCALIZATION OF SULFONATEDmeso‐TETRAPHENYLPORPHINES IN NHIK 3025 CELLS AND EFFECTS OF DOSE FRACTIONATION

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Abstract
Abstract—Human cervix carcinoma cells of the line NHIK 3025 were incubated for 18 h with sulfonatedmeso‐tetraphenylporphines (TPPSnwheren= 1, 2a, 2o or 4) followed by 1 h in sensitizer‐free medium and then exposed to light. The fluorescing fraction of TPPS4, TPPS2oand TPPS2ahas recently been shown to be located intracellularly in extracellular granules which are intracellularly localized in a similar pattern as acridine orange‐stained granules, assumed to be endosomes and lysosomes (Berg, K., A. Western, J. Bommer and J. Moan.Photochem. Photobiol.52, 481–487). Light exposure induced a relocalization of TPPS4from its granular pattern to mainly the nuclear area while TPPS2oand TPPS2arelocalized mainly to cytoplasmic areas. After the light‐induced relocalization TPPS4became less efficient in sensitizing photoinactivation of cells as measured per fluorescing cellbound TPPS4molecules while TPPS2aand TPPS2obecame more efficient. These changes were independent of the extracellular concentration of TPPSnapplied to the cells, except for cells incubated with 75 μg/mL TPPS4. These cells became more sensitive to light after a light exposure inactivating 20% of the cells. This increased photosensitivity seems to be related to a 2–2.5 fold increase in the amount of fluorescing cellbound TPPS4induced by the first light exposure.