Release of ATP induced by hypertonic solutions in Xenopus oocytes.
ATP mediates intercellular communication. Mechanical stress and changes in cell volume induce ATP release from various cell types, both secretory and non-secretory. In the present study, we stressed Xenopus oocytes with a hypertonic solution enriched in mannitol (300 mM). We measured simultaneously ATP release and ionic currents from a single oocyte. A decrease in cell volume, the activation of an inward current and ATP release were coincident. We found two components of ATP release: the first was associated with granule or vesicle exocytosis, because it was inhibited by tetanus neurotoxin, and the second was related to the inward current. A single exponential described the correlation between ATP release and the hypertonic-activated current. Gadolinium ions, which block mechanically activated ionic channels, inhibited the ATP release and the inward current but did not affect the decrease in volume. Oocytes expressing CFTR (cystic fibrosis transmembrane regulator) released ATP under hypertonic shock, but ATP release was significantly inhibited in the first component: that related to granule exocytosis. Since the ATP measured is the balance between ATP release and ATP degradation by ecto-enzymes, we measured the nucleoside triphosphate diphosphohydrolase (NTPDase) activity of the oocyte surface during osmotic stress, as the calcium-dependent hydrolysis of ATP, which was inhibited by more than 50 % in hypertonic conditions. The best-characterized membrane protein showing NTPDase activity is CD39. Oocytes injected with an antisense oligonucleotide complementary to CD39 mRNA released less ATP and showed a lower amplitude in the inward current than those oocytes injected with water.
Aleu
Jordi
J
Laboratory of Molecular and Cellular Neurobiology, Department of Cell Biology, Medical School, Hospital of Bellvitge, University of Barcelona-Campus of Bellvitge, Feixa Llarga s/n, L' Hospitalet de Llobregat, E-08907 Spain.
Martín-Satué
Mireia
M
Navarro
Piedad
P
Pérez de Lara
Ivanna
I
Bahima
Laia
L
Marsal
Jordi
J
Solsona
Carles
C
D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D004234:Diuretics, Osmotic / Q000494:pharmacology; D005089:Exocytosis / Q000502:physiology; D005260:Female; D006982:Hypertonic Solutions / Q000494:pharmacology*; D008353:Mannitol / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D008666:Metalloendopeptidases / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D009997:Osmotic Pressure; D018408:Patch-Clamp Techniques; D013744:Tetanus Toxin / Q000494:pharmacology; D014982:Xenopus laevis
D004234:Diuretics, Osmotic; D006982:Hypertonic Solutions; D013744:Tetanus Toxin; C035979:tetanospasmin; D008353:Mannitol; D000255:Adenosine Triphosphate; D008666:Metalloendopeptidases