Ca2+ influx induced by photodynamic action in human cerebral glioma (U-87 MG) cells: possible involvement of a calcium channel.
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+]i. 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.
Department of Biophysics, National Institute of Mental Health and Neurosciences, Bangalore, India.
P G
PG
Joshi
K
K
Joshi
S
S
Mishra
N B
NB
Joshi
D001692:Biological Transport / Q000187:drug effects / Q000528:radiation effects; D001932:Brain Neoplasms / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D004110:Diltiazem / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005910:Glioma / Q000378:metabolism*; D017324:Hematoporphyrin Derivative / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008027:Light; D010778:Photochemotherapy; D014407:Tumor Cells, Cultured
D015220:Calcium Channels; D017324:Hematoporphyrin Derivative; D004110:Diltiazem; D002118:Calcium