Properties of the apamin-sensitive component of Ca2+-dependent K+ current in smooth muscle cells of the guinea pigtaenia coli

Povstyan, A. V.; Zima, A. V.; Harhun, Maksym I.; Shuba, M. F.

doi:10.1007/bf02515170

Cited by 6 publications

(6 citation statements)

References 20 publications

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“…The former study demonstrated a small contribution of the current via these channels in the total outward transmembrane ion current of murine colonic SMC. These results agree with our earlier data [7,8] current was shown to be below 5-15%. In contrast, Vogalis and Goyal [6] found rather significant current via the apamin-sensitive SKc, channels in the murine ileal SMC.…”

Section: Introductionsupporting

confidence: 96%

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Membrane mechanisms of the effects of apamin on ion currents in smooth muscle cells

2000

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Section: Introductionsupporting

confidence: 96%

“…Details on isolation of viable myocytes, experimental set-up, and patch-clamping procedures have been described earlier [7,8]. The holding potential was maintained at -60 mV throughout the experiments.…”

Section: Methodsmentioning

confidence: 99%

Membrane mechanisms of the effects of apamin on ion currents in smooth muscle cells

2000

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“…As is known, TEA in a concentration of 1 mM completely blocks the ВK Са [4,13], while the SK Са are not blocked by this agent even at considerably higher concentrations (4 mM) [6]. Application of 1 mM TEA (n = 6) led to a significant decrease in the amplitude of outward current induced by a shift of the membrane potential from the holding level of -50 mV to +40 mV.…”

Section: Resultsmentioning

confidence: 95%

“…Therefore, calcium-dependent potassium channels can be divided into channels of big (100 to 250 pS) and small (up to 18 pS) unitary conductance, BK Ca and SK Ca , respectively. The BK Ca channels are sensitive to the blocking effect of charibdotoxin [2][3][4], while the SK Ca channels are sensitive to apamin [2,5,6]. Some authors identify three subtypes of such channels by adding the group with the intermediate conductance (18 to 90 pS), IK Са [2,[7][8][9].…”

Section: Introductionmentioning

confidence: 97%

D-Tubocurarine-Sensitive Component of Calcium-Dependent Potassium Current in Guinea Pig Taenia Coli Myocytes

2005

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Using a patch-clamp technique in the whole-cell configuration, we studied transmembrane ion currents in isolated single smooth muscle cells of the guinea pig taenia coli. A depolarizing step shift of the membrane potential from -50 mV was accompanied by the appearance of an outward current. Application of d-tubocurarine (d-TK) or a nonselective blocker of voltage-dependent potassium channels, tetraethylammonium (TEA), led to a decrease in the outward current. Application of d-TK against the background of the action of TEA additionally decreased the outward current. Analysis of the currentvoltage (I-V) relationships of the d-TK-sensitive current showed that this current is practically voltageindependent. At the same time, an inflection of the I-V curve of the potassium current within the segment of maximum activation of the voltage-dependent potassium current is indicative of the sensitivity of this current to the intracellular Ca 2+ concentration. Therefore, the calcium-activated potassium current through small-conductance calcium-dependent potassium channels includes a d-TK-sensitive voltage-independent component. Using depolarizing shifts of the membrane potential, we observed high-and low-amplitude spontaneous outward currents (SOCs) in many studied cells, i.e., the effect of an increase in the conductance of calcium-dependent potassium channels as a result of periodic release of Ca 2+ from the intracellular stores. Application of d-TK led to a decrease in the frequency of low-amplitude SOCs and exerted nearly no influence on the high-amplitude SOCs under study.

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“…This group is usually divided into channels of big conductance (BK Са ; the conductance of a unitary channel 100 to 250 pS; channels sensitive to the blocking actions of tetraethylammonium, TEA, and charibdotoxin [5][6][7][8]) and channels of small conductance (SK Са , below 18 pS, channels blocked by apamin and d-tubocurarine [5,[9][10][11][12] [13,14]. At present, there are no highly selective blockers for this channel type.…”

Section: Introductionmentioning

confidence: 98%

Characteristics of paxilline-sensitive calcium-dependent potassium current in isolated intestine myocytes

2007

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An inward current in smooth muscle cells (SMCs) of the taenia coli is known to be transferred via potassium channels and nonselective cation channels. The outward current is of a potassium nature and includes several components, Ca-dependent potassium current (I K(Ca) ) and delayed rectifying potassium current (I K(V) ) in particular. Applications of 100 nM paxilline to SMCs of the guinea-pig taenia coli suppressed considerably the outward current and decreased its oscillations; the effect of paxilline reached its maximum in 2 to 3 min from the beginning of application. Analysis of the current-voltage (I-V) relationship observed under conditions of such applications showed that the paxilline-sensitive current is highly dependent on the intracellular Ca 2+ concentration; a change in the I-V slope within a segment of the maximum activation of the calcium current is indicative of this peculiarity. Application of paxilline against the background of the action of 1 mM tetraethylammonium (a nonselective blocker of potassium channels) evoked no additional suppression of the outward current. In most cells, we observed spontaneous outward currents (SOCs). Application of 100 nM paxilline nearly completely blocked high-amplitude SOCs (>10 pA) formed due to activation of big-conductance Ca-dependent potassium channels. At the same time, the frequency of smallamplitude SOCs (<10 pA) practically did not change. Thus, according to the pharmacological and time characteristics, voltage dependence, and sensitivity to the intracellular Ca 2+ concentration, we identified a voltage-operated paxilline-sensitive component in I K(Ca) that is transferred via big-conductance Ca-dependent potassium channels.

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Properties of the apamin-sensitive component of Ca2+-dependent K+ current in smooth muscle cells of the guinea pigtaenia coli

Cited by 6 publications

References 20 publications

Membrane mechanisms of the effects of apamin on ion currents in smooth muscle cells

Membrane mechanisms of the effects of apamin on ion currents in smooth muscle cells

D-Tubocurarine-Sensitive Component of Calcium-Dependent Potassium Current in Guinea Pig Taenia Coli Myocytes

Characteristics of paxilline-sensitive calcium-dependent potassium current in isolated intestine myocytes

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