The role of bivalent cations and choline in ATP induced apoptosis via P2Z purinoceptor was investigated in human leukemic lymphocytes. In vitro exposure of leukemic lymphocytes with P2Z receptors to 1 mmol/L ATP or 0 1 mmol/L benzoylbenzoic ATP（BzATP） for 8 h in the presence of choline

1 mmol/L Mg 2+ or other bivalent cations

and ATP induced DNA breaks

associated with apoptosis were quantified by TdT assay. We observed that （1） Extracellular Mg 2+ or Ca 2+ stimulated ATP induced DNA fragmentation in a dose dependent manner

and the compatible evidence was provided by the inhibition of ATP induced DNA fragmentation in the present of EGTA or EDTA; （2） ATP induced DNA fragmentation was completely inhibited by 1 mmol/L Zn 2+ ;（3）ATP induced DNA breaks were not affected by Ba 2+

Sr 2+

Co 2+ when they were substituted for extracellular Mg 2+ or Ca 2+ ;（4）Choline

an inhibitor of phospholipase D（PLD） stimulated by ATP through P2Z receptor in human lymphocytes

was also a partial inhibitor of ATP induced DNA fragmentation

and the results were confirmed by flow cytometric analysis （FCA）; （5）ATP induced DNA fragmentation was completely obliterated when the temperature was lower than 10℃. These results suggest that the endonuclease and PLD may be involved in ATP induced apoptosis in human lymphocytes via P2Z receptor.