Blocking agents of Ca2+-activated K+ channels in cultured medullary thick ascending limb cells.

S. E. Guggino, William B Guggino, N. Green, B. Sacktor

Research output: Contribution to journalArticle

Abstract

Ca2+-activated K+ channels with estimated single channel conductances of 127 +/- 2 pS were identified in the apical cell membrane of clone A3 of cultured medullary thick ascending limb (MTAL) cells. Both Ba2+ and the scorpion toxin, charybdotoxin (CTX), are slow blockers of the channels. An application of 0.1 microM Ba2+ to the intracellular face caused a 50% reduction in fractional open time (fv). Ba2+ block is both concentration and voltage dependent. Concentrations of CTX as low as 2 nM in the extracellular solution caused a significant reduction in fv. Tetraethylammonium (TEA) and quinine are fast blockers of Ca2+-activated K+ channels in MTAL cells. TEA, 400 microM, in the extracellular solution caused a voltage-dependent reduction in channel amplitude, whereas it takes 10 mM in the intracellular solution to reduce channel amplitude by 30%. Micromolar amounts of quinine applied to the intracellular face caused the channels to flicker rapidly between open and blocked states. These results suggest that K+ channels in MTAL cells are homologous to those found in muscle cells, and that these blocking agents may be used to probe the nature of K+ conductances in several nephron segments.

Original languageEnglish (US)
JournalThe American journal of physiology
Volume252
Issue number2 Pt 1
StatePublished - Feb 1987
Externally publishedYes

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Calcium-Activated Potassium Channels
Charybdotoxin
Tetraethylammonium
Quinine
Extremities
Scorpions
Nephrons
Muscle Cells
Clone Cells
Cell Membrane

ASJC Scopus subject areas

  • Medicine(all)

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Blocking agents of Ca2+-activated K+ channels in cultured medullary thick ascending limb cells. / Guggino, S. E.; Guggino, William B; Green, N.; Sacktor, B.

In: The American journal of physiology, Vol. 252, No. 2 Pt 1, 02.1987.

Research output: Contribution to journalArticle

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