[The blocking effects of extracellular Mn2+ on the inward rectifier potassium channel (IRK1)].
OBJECTIVE
Two-microelectrode voltage clamp (TEV) method was used to study the blocking effects of extracellular Mn2+ on the inward rectifier potassium channel (IRK1) expressed in the Xenopus oocytes.


RESULTS
Mn2+ can concentration-, time- and vol-tage dependently block IRK1 instantaneous currents (2 ms after voltage applied). Mn2+ has almost no effect on the gating property of IRK1. IRK1 can not permeate Mn2+ because reverse potential did not changed. External Mn2+ can inhibit IRK1 macroscopic currents more powerfully when external Mn2+ concentration is lower and external Mn2+ can increases standard chord conductance of IRK1.


CONCLUSIONS
External Mn2+ works through surface potential mechanism. Ba2+ is considered as one fast open channel blocker of IRK1 and three exponential fitting results indicates that external Mn2+ can compete with Ba2+ in the same binding site in IRK1 when external Ba2+ concentration is 30 mumol/L. These mean two different mechanisms about external Mn2+ blocking exist.
Department of Physiology, Basic Science Institute, the Fourth Military Medical University, Xi'an 710032.
A
A
Xie
Y M
YM
Zang
M Z
MZ
Zhu
D000818:Animals; D002478:Cells, Cultured; D005260:Female; D008345:Manganese / Q000494:pharmacology*; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects*; D014981:Xenopus
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D008345:Manganese