Biphasic effect of extracellular ATP on the membrane potential of mouse thymocytes.
Extracellular ATP induced changes in the membrane potential of thymocytes from BALB/c mice were analyzed. At concentrations below 0.1 mM, ATP hyperpolarizes the cell membrane on the time scale of development of the Ca(2+)-signal. After a longer time hyperpolarization turns to depolarization. ATP concentrations higher than 0.5 mM caused rapid depolarization without previous hyperpolarization. Verapamil, quinine or the absence of extracellular Ca2+ blocked the hyperpolarization by ATP. In Na(+)-free medium the magnitude of depolarization decreased. Our data suggest a contribution of Ca(2+)-activated K+ channels to the hyperpolarizing effect of ATP at lower concentrations. The direction of membrane potential changes is determined presumably by a sensitive balance of ATP-receptor mediated Ca(2+)- and Na(+)-influx and the Ca(2+)-activated K(+)-channel activity.
Matkó
J
J
Department of Biophysics, University Medical School, Debrecen, Hungary.
Nagy
P
P
Panyi
G
G
Vereb
G
G
Bene
L
L
Mátyus
L
L
Damjanovich
S
S
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D011803:Quinine / Q000494:pharmacology; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology
D000255:Adenosine Triphosphate; D011803:Quinine; D014700:Verapamil