Voltage-dependent ionic conductances in the human malignant astrocytoma cell line U87-MG.
Although the human malignant astrocytoma cell line U87-MG has been used in numerous studies, few findings are available on the properties of its membrane ion conductances. Characterization of the ion channels expressed in these cells will make it possible to study membrane ion conductance changes when a receptor is activated by its ligand. This will help to elucidate the functional properties of these receptors and their signal-transduction pathways in pathophysiological events. This work studied the voltage-dependent ionic conductances of U87-MG cells using the Whole-Cell Recording patch-clamp technique. Six types of voltage-dependent ionic currents were identified: (i) a TEA-, 4-AP- and CTX-sensitive Ca2+-dependent K+ current, (ii) a transient K+ current inhibited by 4-AP, (iii) an inwardly rectifying K+ current blocked by Ba2+ and 4-AP, (iv) a DIDS- and SITS-sensitive Cl- current, (v) a TTX-sensitive Na+ conductance and (vi) a L-type Ca2+ conductance activated by BayK-8644 and inhibited by Ni and the L-type Ca2+ channel inhibitor, nifedipine. In addition, electrical depolarizations elicited inward currents due to voltage-independent, Ca2+-dependent K+ influx against the electrochemical gradient, probably via an ouabain-sensitive Na+-K+ pump.
Ducret
Thomas
T
Institut National de la Santé et de la Recherche Médicale EMI 0347 Signalisation et Mécanismes Moléculaires de l'Apoptose, Centre National de le Recherche Scientifique UMR 5543, Université de Bordeaux 2, 33076 Bordeaux cédex, France.
Vacher
Anne-Marie
AM
Vacher
Pierre
P
D001254:Astrocytoma / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D004553:Electric Conductivity; D006801:Humans; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
D002712:Chlorides; D007473:Ion Channels; D012964:Sodium; D011188:Potassium