RESUMO
Extracellular ATP elicits various biological responses and plays a significant role in physiological regulation. Recently, ATP-induced growth inhibitions were reported in some tumor cell lines, but these effects and mechanisms are not well known. This study was conducted to investigate ATP-induced growth inhibition in mouse leukemic (P388D,) cells. ATP inhibited cell growth in a dose-dependent manner as analyzed by MTS assay (IC50: 33.1 muM). Nucleotides other than ATP, such as ADP (37.5 muM) and AMP (33.2 muM) had the same effects as ATP, but adenosine (57.8 muM) showed less effect than ATP. ATP attenuated the cells in G0/G1 and G2/M phases, but increased those in S phase in flow cytometric analysis. Hypodiploid cells (A0), the presumptive findings of apoptosis, were found among the ATP-treated cells. ATP induced DNA fragmentation into 180 ~ 200 bps as measured by electrophoresis. Some apoptotic cells were stained by TUNEL method. ATP increased the intracellular free Ca++ concentration ((Ca++)i) and the increment of (Ca++)i was caused by influx from the extracellular space. These results suggest that extracellular ATP induces growth inhibition through apoptosis.