Cell swelling-induced ATP release and gadolinium-sensitive channels.
ATP release induced by hypotonic swelling is an ubiquitous phenomenon in eukaryotic cells, but its underlying mechanisms are poorly defined. A mechanosensitive (MS) ATP channel has been implicated because gadolinium (Gd(3+)), an inhibitor of stretch-activated channels, suppressed ATP efflux monitored by luciferase bioluminescence. We examined the effect of Gd(3+) on luciferase bioluminescence and on ATP efflux from hypotonically swollen cells. We found that luciferase was inhibited by < or =10 microM Gd(3+), and this may have contributed to the previously reported inhibition of ATP release. In ATP efflux experiments, luciferase inhibition could be prevented by chelating Gd(3+) with EGTA before luminometric ATP determinations. Using this approach, we found that 10-100 microM Gd(3+), i.e., concentrations typically used to block MS channels, actually stimulated hypotonically induced ATP release from fibroblasts. Inhibition of ATP release required at least 500, 200, or 100 microM Gd(3+) for fibroblasts, A549 cells, and 16HBE14o(-) cells, respectively. Such biphasic and cell-specific effects of Gd(3+) are most consistent with its action on membrane lipids and membrane-dependent processes such as exocytosis.
Boudreault
Francis
F
Centre hospitalier de l'Université de Montréal and Department of Medicine, Université de Montréal, Montréal, Québec, Canada H2W 1T8.
Grygorczyk
Ryszard
R
D016475:3T3 Cells; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000328:Adult; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002277:Carcinoma; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D048429:Cell Size; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology*; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D007473:Ion Channels / Q000502:physiology*; D008156:Luciferases; D008163:Luminescent Measurements; D008175:Lung Neoplasms; D051379:Mice; D009997:Osmotic Pressure; D014407:Tumor Cells, Cultured; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
D002614:Chelating Agents; D007038:Hypotonic Solutions; D007473:Ion Channels; D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D005682:Gadolinium; D008156:Luciferases