Figure 7.

Cisplatin (CDDP)-induced increase of apoptotic rate is reduced in HeLa-S3 but not in U2-OS cells, when no calcium is added or IP₃ receptors are blocked. (a) Apoptotic rate under different conditions in normal calcium (1.8 mM) containing medium. In HeLa-S3 cells, cisplatin increased apoptotic rate (^***P<0.001 compared to control) and this increase was significantly reduced by 2-APB (^***P<0.001; means±s.d.). (b) Apoptotic rates with calcium-free incubation medium are not significantly changed by cisplatin. (c) Apoptotic rate in U2-OS cells incubated in normal calcium medium is also unchanged after cisplatin. (d) Cell viability test. The number of living cells is decreased significantly (^*P<0.05; means±s.d.) beginning at 72 h of exposure to 1 μM cisplatin. Note time dependence of cytotoxicity. IP₃ receptors, inositol-1,4,5-trisphosphate receptors; 2-APB, 2-aminoethoxydiphenyl borate.