Involvement of intracellular Ca2+ and K+ in dissipation of the mitochondrial membrane potential and cell death induced by extracellular ATP in hepatocytes.
Isolated rat hepatocytes were incubated with extracellular ATP to induce a prolonged increase in intracellular Ca2+ ([Ca2+]i) and a loss of viability within 2 h. By using video-intensified fluorescence microscopy, the effects of exposure to extracellular ATP on [Ca2+]i, mitochondrial membrane potential (MMP) and cell viability were determined simultaneously in individual living hepatocytes. The increase in [Ca2+]i on exposure to ATP was followed by a decreasing MMP; there were big differences between individual cells. Complete loss of the MMP occurred before cell death was observed. Omission of K+ from the incubation medium decreased the cytotoxicity of ATP; under these conditions, intracellular K+ was decreased by more than 80%. Treatment with nigericin also depleted intracellular K+ and decreased ATP-induced toxicity. Protection against loss of viability by means of a decrease in intracellular [K+] was reflected by maintenance of the MMP. These observations suggest that ATP-induced cell death may be caused by a mechanism that has been described for isolated mitochondria: after an increase in Ca2+ levels, a K+ influx into mitochondria is induced, which finally disrupts the MMP and leads to cell death.
Zoeteweij
J P
JP
Division of Toxicology, University of Leiden, The Netherlands.
van de Water
B
B
de Bont
H J
HJ
Mulder
G J
GJ
Nagelkerke
J F
JF
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology*; D003600:Cytosol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000502:physiology*; D007700:Kinetics; D008099:Liver / Q000502:physiology* / Q000648:ultrastructure; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000648:ultrastructure*; D009550:Nigericin / Q000494:pharmacology; D011188:Potassium / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D000255:Adenosine Triphosphate; D009550:Nigericin; D011188:Potassium; D002118:Calcium