Ca2+-activated K+ channels from rabbit kidney medullary thick ascending limb cells expressed in Xenopus oocytes

L. Lu, C. Montrose-Rafizadeh, W. B. Guggino

Research output: Contribution to journalArticlepeer-review

Abstract

Ca2+-activated K+ channels are present in muscle, nerve, pancreas, macrophages, and renal cells. They are important in such diverse functions as neurotransmitter release, muscle excitability, pancreatic secretion, and cell volume regulation. Although much is known about the biophysics of Ca2+-activated K+ channels, the molecular structure, cDNA and amino acid sequences are unknown. We injected size-fractionated mRNA isolated from cultured rabbit kidney medullary thick ascending limb cells in Xenopus oocytes and observed newly expressed K+ currents using two-microelectrode voltage-clamp technique. The expressed K+ are currents are Ca2+ dependent and inhibited by charybdotoxin, a specific blocker of Ca2+-activated K+ channels. Amplitudes of the current ranged from 30 nA to more than 1 μA at a membrane potential of +30 mV. Reversal potential of the current suggested a K+-selective channel. The peak activity of Ca2+-activated K+ channels were observed in fractions corresponding to a message RNA with size of approximately 4.5 kilobases.

Original languageEnglish (US)
Pages (from-to)16190-16194
Number of pages5
JournalJournal of Biological Chemistry
Volume265
Issue number27
StatePublished - 1990

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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