The role of a purinergic P2z receptor in calcium‐dependent cell killing of isolated rat hepatocytes by extracellular adenosine triphosphate

Extracellular adenosine triphosphate (ATPo) (0.4 mmol/L), a P2‐purinergic receptor agonist, induces cytolysis in several cell types including isolated rat hepatocytes. In this study, we investigated the P2‐receptor involved in ATPo‐induced, Ca2+‐dependent cytotoxicity in hepatocytes. Pretreatment of hepatocytes with oxidized ATP, a P2z‐receptor antagonist, or complexation of ATP4− (the agonist for the P2z‐receptor) with an excess of Mg2+, prevented ATPo‐induced cell death. Both protective treatments also prevented the development of a sustained high intracellular Ca2+ concentration as well as the subsequent accumulation of inorganic phosphate (Pi). The P2z‐receptor agonist 3′‐O‐'(4‐benzoylbenzoyl)‐ATP (BzATP) was twofold more potent than ATP in eliciting cytolysis, which was preceded by a sustained high intracellular Ca2+ concentration; pretreatment with oxidized ATP prevented both the increase in the intracellular Ca2+ concentration and cell death. Prevention of ATPo‐induced cell death, as well as the increases in the intracellular Ca2+ concentration and inorganic phosphate (Pi) was also achieved by decreasing the pHo to 6.9. Together the findings indicate that Ca2+‐dependent cell killing by extracellular ATP in hepatocytes is mediated by a P2z‐receptor. The cytolytic effects correlated specifically with a secondary “late” increase in the intracellular Ca2+ concentration.