Characterization of a newly found stretch-activated K(Ca,ATP) channel in cultured chick ventricular myocytes

Takashi Kawakubo, Keiji Naruse, Tatsuaki Matsubara, Nigishi Hotta, Masahiro Sokabe

Research output: Contribution to journalArticle

65 Citations (Scopus)

Abstract

With the use of the patch-clamp technique, five kinds of stretch- activated (SA) ion channels were identified on the basis of their single- channel conductances and ion selectivities in cultured chick ventricular myocytes. Because a high-conductance K+- selective channel predominated among these channels, we concentrated on characterizing its properties mostly using excised inside-out patches. With 145 mM KCl solution in the pipette and the bath, the channel had a conductance of 199.8 ± 8.2 pS (n = 22). The ion selectivities among K+, Na+, Ca2+, and Cl- as estimated from their permeability ratios were P(Na)/P(K) = 0.03, P(Ca)/P(K) = 0.025, and P(Cl)/P(K) = 0.026. The probability of the channel being open (P(o)) increased with the Ca2+ concentration in the bath ([Ca2+](b); dissociation constant K(d) = 0.51 μM at +30 mV) and membrane potential (voltage at half-maximal P(o) = 39.4 mV at 0.35 μM [Ca2+](b)). The channel was blocked by gadolinium, tetraethylammonium, and charybdotoxin from the extracellular surface and, consequently, was identified as a Ca2+-activated K+ (K(Ca)) channel type. The channel was also reversibly activated by ATP applied to the intracellular surface (K(d) = 0.74 mM at 0.10 μM [Ca2+](b) at +30 mV). From these data taken together, we concluded that the channel is a new type of K(Ca) channel that could be designated as an 'SA K(Ca,ATP) channel.' To our knowledge, this is the first report of K(Ca) channel in heart cells.

Original languageEnglish
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume276
Issue number6 45-6
Publication statusPublished - Jun 1999
Externally publishedYes

Fingerprint

Baths
Ion Channels
Muscle Cells
Adenosine Triphosphate
Charybdotoxin
Tetraethylammonium
Gadolinium
Patch-Clamp Techniques
Membrane Potentials
Permeability
Ions

Keywords

  • Adenosine 5'-triphosphate-activated channel
  • Calcium-activated potassium channel
  • Patch clamp
  • Stretch-activated channel

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Cite this

Characterization of a newly found stretch-activated K(Ca,ATP) channel in cultured chick ventricular myocytes. / Kawakubo, Takashi; Naruse, Keiji; Matsubara, Tatsuaki; Hotta, Nigishi; Sokabe, Masahiro.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 276, No. 6 45-6, 06.1999.

Research output: Contribution to journalArticle

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T1 - Characterization of a newly found stretch-activated K(Ca,ATP) channel in cultured chick ventricular myocytes

AU - Kawakubo, Takashi

AU - Naruse, Keiji

AU - Matsubara, Tatsuaki

AU - Hotta, Nigishi

AU - Sokabe, Masahiro

PY - 1999/6

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N2 - With the use of the patch-clamp technique, five kinds of stretch- activated (SA) ion channels were identified on the basis of their single- channel conductances and ion selectivities in cultured chick ventricular myocytes. Because a high-conductance K+- selective channel predominated among these channels, we concentrated on characterizing its properties mostly using excised inside-out patches. With 145 mM KCl solution in the pipette and the bath, the channel had a conductance of 199.8 ± 8.2 pS (n = 22). The ion selectivities among K+, Na+, Ca2+, and Cl- as estimated from their permeability ratios were P(Na)/P(K) = 0.03, P(Ca)/P(K) = 0.025, and P(Cl)/P(K) = 0.026. The probability of the channel being open (P(o)) increased with the Ca2+ concentration in the bath ([Ca2+](b); dissociation constant K(d) = 0.51 μM at +30 mV) and membrane potential (voltage at half-maximal P(o) = 39.4 mV at 0.35 μM [Ca2+](b)). The channel was blocked by gadolinium, tetraethylammonium, and charybdotoxin from the extracellular surface and, consequently, was identified as a Ca2+-activated K+ (K(Ca)) channel type. The channel was also reversibly activated by ATP applied to the intracellular surface (K(d) = 0.74 mM at 0.10 μM [Ca2+](b) at +30 mV). From these data taken together, we concluded that the channel is a new type of K(Ca) channel that could be designated as an 'SA K(Ca,ATP) channel.' To our knowledge, this is the first report of K(Ca) channel in heart cells.

AB - With the use of the patch-clamp technique, five kinds of stretch- activated (SA) ion channels were identified on the basis of their single- channel conductances and ion selectivities in cultured chick ventricular myocytes. Because a high-conductance K+- selective channel predominated among these channels, we concentrated on characterizing its properties mostly using excised inside-out patches. With 145 mM KCl solution in the pipette and the bath, the channel had a conductance of 199.8 ± 8.2 pS (n = 22). The ion selectivities among K+, Na+, Ca2+, and Cl- as estimated from their permeability ratios were P(Na)/P(K) = 0.03, P(Ca)/P(K) = 0.025, and P(Cl)/P(K) = 0.026. The probability of the channel being open (P(o)) increased with the Ca2+ concentration in the bath ([Ca2+](b); dissociation constant K(d) = 0.51 μM at +30 mV) and membrane potential (voltage at half-maximal P(o) = 39.4 mV at 0.35 μM [Ca2+](b)). The channel was blocked by gadolinium, tetraethylammonium, and charybdotoxin from the extracellular surface and, consequently, was identified as a Ca2+-activated K+ (K(Ca)) channel type. The channel was also reversibly activated by ATP applied to the intracellular surface (K(d) = 0.74 mM at 0.10 μM [Ca2+](b) at +30 mV). From these data taken together, we concluded that the channel is a new type of K(Ca) channel that could be designated as an 'SA K(Ca,ATP) channel.' To our knowledge, this is the first report of K(Ca) channel in heart cells.

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