Extracellular ATP4- permeabilizes thymocytes not only to cations but also to low-molecular-weight solutes.
Extracellular ATP increases the free cytosolic calcium concentration ([Ca2+]i) of thymocytes by changing the membrane permeability to divalent cations: (1) no [Ca2+]i elevation is observed in the absence of extracellular calcium and (2) ATP also promotes Mn2+ entry into thymocytes, as shown by a stimulated quench of the fluorescence of Quin2-loaded cells. Using 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5- hexatriene, a dye which usually does not pass through membranes, we showed that ATP permeabilizes thymocyte membranes not only to cations but also to low-molecular-weight solutes. The ATP effect is dose-dependent, specific and reversible; ATP4- appears to be the active species and probably acts through specific receptor(s). Both medullary and cortical thymocytes respond to ATP whereas splenocytes do not; this shows that the ATP effect is restricted to certain populations of lymphocytes. The thymoma-derived cell line, EL-4, the permeability of which is also sensitive to ATP, could provide a useful model for studying the putative ATP4- receptor(s) of thymocytes.
el-Moatassim
C
C
Laboratoire de Biologie Cellulaire, INSERM U65, USTL, Faculté de Pharmacie, Montpellier, France.
Mani
J C
JC
Dornand
J
J
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002412:Cations / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects*; D051379:Mice; D008970:Molecular Weight; D013050:Spectrometry, Fluorescence; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism
D002412:Cations; D000255:Adenosine Triphosphate