Ca2+ INFLUX INDUCED BY PHOTODYNAMIC ACTION IN HUMAN CEREBRAL GLIOMA (U-87 MG) CELLS: POSSIBLE INVOLVEMENT OF A CALCIUM CHANNEL |
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Authors: | Preeti G Joshi Kunju Joshi Sudha Mishra Nanda B Joshi |
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Institution: | Department of Biophysics, National Institute of Mental Health and Neurosciences, Bangalore 560 029, India |
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Abstract: | Abstract The plasma membrane has been implicated as a critical target of photodynamic action on cells. We have observed that the photosensitization of human cerebral glioma (U-87 MG) cells by hematoporphyrin derivative (HpD) causes a large increase in intracellular calcium Ca2+]. This increase in Ca2+]i was solely due to the influx of extracellular Ca2+ through the plasma membrane and showed a dependence on HpD concentration, light dose and concentration of calcium in the extracellular medium. The magnitude of the Ca2+ influx decreased with increasing postirradiation time, which suggests that the cell membrane partially recovers from the photodynamic injury. The photoinduced Ca2+ influx was inhibited by the Ca2+ channel blocker diltiazem and the reducing agent dithioerythritol. These findings are discussed in terms of possible activation of a Ca2+ channel as a result of photosensitization. |
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