Cytolytic effects and biochemical changes induced by extracellular ATP to isolated hepatocytes.

Cell death, as estimated by the release of lactate dehydrogenase (LDH), was induced by incubating isolated hepatocytes for 60 min in the presence of extracellular ATP (ecATP), while AMP, adenosine, GTP and UTP were without any significant effects, even when tested at 3 mM (final concentration). At such a concentration, the release of LDH induced by ecATP, but also by ecADP, reached almost 50% and 30%, respectively. Since UTP and GTP (which have no lytic effects) were able to activate phosphorylase a at the same rate as ATP, we excluded the possibility that an increase of free cytosolic Ca2+ triggers the onset of a process leading to cell lysis. Moreover, such a lytic ability of ecATP (1.7 mM) can not be the result of a previous complexation of ionic iron (making it catalytically available for a Fenton reaction), because Desferal, a strong iron chelator, did not modify the cytolytic effect of the ecATP observed after 60 min of incubation. A major cellular function such as protein synthesis was impaired in a dose-dependent way by incubating hepatocytes during 60 min in the presence of ecATP. The inhibition was already observed at 0.1 mM ecATP, a dose without any effect on cell viability. The biological relevance of such metabolic impairment, however, remains to be elucidated.