Intracellular Ca2+ concentration change of T24 cell under irradiation in the presence of TiO2 ultrafine particles.
We reported that malignant cells are inactivated by photo-excited TiO2 particles (Cai, R.-X., et al. (1992) Cancer Res. 52, 2346-2348). In the present study, the process of cell death of a human bladder cell line T24 with the irradiated TiO2 was investigated by monitoring the time course change in intracellular calcium concentration ([Ca2+]i) under UV irradiation using calcium fluorescence indicator, fura-2. In the presence of photo-excited TiO2 particles (100 micrograms/ml), [Ca2+]i showed a rapid two-step increase; while in the absence of TiO2, it exhibited only a slight and monotonous increase or maintained a constant level. The rapid elevation of [Ca2+]i in the presence of photo-excited TiO2 particles was caused by the influx of extracellular Ca2+ through the plasma membrane and cell death occurred only after the second rapid elevation of [Ca2+]i. These results suggested that the cell membrane permeability to Ca2+ was promoted prior to cell death.
Sakai
H
H
Department of Synthetic Chemistry, Faculty of Engineering, University of Tokyo, Japan.
Ito
E
E
Cai
R X
RX
Yoshioka
T
T
Kubota
Y
Y
Hashimoto
K
K
Fujishima
A
A
D002118:Calcium / Q000032:analysis*; D002463:Cell Membrane Permeability; D002470:Cell Survival; D004996:Ethidium; D016257:Fura-2; D006801:Humans; D013997:Time Factors; D014025:Titanium / Q000494:pharmacology* / Q000528:radiation effects; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000648:ultrastructure; D014466:Ultraviolet Rays
C009495:titanium dioxide; D014025:Titanium; D004996:Ethidium; D002118:Calcium; D016257:Fura-2