Nonselective cationic currents elicited by extracellular ATP in human B-lymphocytes.
Adenosine 5'-triphosphate-(ATP)-induced whole-cell currents were studied in human B-lymphocytes, transformed by the Epstein-Barr virus, by means of the tight-seal voltage-clamp technique. During bath application of ATP, the membrane conductance was increased. The change of membrane conductance occurred within milliseconds. The dose response relationship for the ATP(4-)-elicited membrane current (Ip) was fitted by the Hill function with a Hill coefficient of 1 and a KD value of 0.2 mmol/l. Adenosine, as well as the Mg(2+)-bound form of ATP, did not effect the membrane conductance. Ip did not desensitize within 1 min and could be evoked repeatedly up to 100 times in 1 cell in the presence of the G-protein blocker Guanosine 5'-o-(2-thiodiphosphate) (GDP [beta S]). Therefore, it seems that ion channels in form of P2Z-purinoceptors are involved in the observed effects. The permeability (P) sequence for cations carrying Ip was PCa:PK:PCs:PNa:PTRIS = 35:2:1.2:1:0.1. The reversal potential of IP was not changed by substitution of intracellular Cl- for aspartate, indicating that anions are not involved in the purinoceptor-dependent conductance. A single-channel conductance of P2Z-receptor-dependent ion channels of about 3 pS was determined by noise analysis of Ip.
Bretschneider
F
F
Martin-Luther-University Halle-Wittenberg, Julius-Bernstein-Institute for Physiology, Halle/S., Germany.
Klapperstück
M
M
Löhn
M
M
Markwardt
F
F
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D004594:Electrophysiology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D018408:Patch-Clamp Techniques
D007473:Ion Channels; D008024:Ligands; D000255:Adenosine Triphosphate