title: The role of intracellular pH in cell growth arrest induced by ATP.
abstract: In this study, we investigated ionic mechanisms involved in growth arrest induced by extracellular ATP in androgen-independent prostate cancer cells. Extracellular ATP reversibly induced a rapid and sustained intracellular pH (pH(i)) decrease from 7.41 to 7.11. Inhibition of Ca(2+) influx, lowering extracellular Ca(2+), and buffering cytoplasmic Ca(2+) inhibited ATP-induced acidification, thereby demonstrating that acidification is a consequence of Ca(2+) entry. We show that ATP induced reuptake of Ca(2+) by the mitochondria and a transient depolarization of the inner mitochondrial membrane. ATP-induced acidification was reduced after the dissipation of the mitochondrial proton gradient by rotenone and carbonyl cyanide p-trifluoromethoxyphenylhydrazone, after inhibition of Ca(2+) uptake into the mitochondria by ruthenium red, and after inhibition of the F(0)F(1)-ATPase with oligomycin. ATP-induced acidification was not induced by either stimulation of the Cl(-)/HCO(3)(-) exchanger or inhibition of the Na(+)/H(+) exchanger. In addition, intracellular acidification, induced by an ammonium prepulse method, reduced the amount of releasable Ca(2+) from the endoplasmic reticulum, assessed by measuring change in cytosolic Ca(2+) induced by thapsigargin or ATP in a Ca(2+)-free medium. This latter finding reveals cross talk between pH(i) and Ca(2+) homeostasis in which the Ca(2+)-induced intracellular acidification can in turn regulate the amount of Ca(2+) that can be released from the endoplasmic reticulum. Furthermore, pH(i) decrease was capable of reducing cell growth. Taken together, our results suggest that ATP-induced acidification in DU-145 cells results from specific effect of mitochondrial function and is one of the major mechanisms leading to growth arrest induced by ATP.
authors.affiliation: Laboratoire de Physiologie Cellulaire, INSERM EMI 0228, Université des Sciences et Technologies de Lille, Bât. SN3, 59655 Villeneuve d'Ascq Cedex, France. sandrine.humez@univ-lille1.fr
authors.forename: Sandrine
authors.initials: S
authors.lastname: Humez
authors.forename: Michaël
authors.initials: M
authors.lastname: Monet
authors.forename: Fabien
authors.initials: F
authors.lastname: van Coppenolle
authors.forename: Philippe
authors.initials: P
authors.lastname: Delcourt
authors.forename: Natalia
authors.initials: N
authors.lastname: Prevarskaya
mesh_terms: D000143:Acids / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D027963:Chloride-Bicarbonate Antiporters / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008928:Mitochondria / Q000201:enzymology; D011471:Prostatic Neoplasms; D006180:Proton-Translocating ATPases / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D000143:Acids; D027963:Chloride-Bicarbonate Antiporters; D017923:Sodium-Hydrogen Exchangers; D000255:Adenosine Triphosphate; D010738:Type C Phospholipases; D006180:Proton-Translocating ATPases; D002118:Calcium