Ionic channels in smooth muscle studied with patch-clamp methods.

Tomita, Tadao

doi:10.2170/jjphysiol.38.1

Cited by 33 publications

(8 citation statements)

References 63 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both are instantaneous, have almost ohmic conductance from -160 to 0 mV, th*&shold potential of near -50 mV, and O . In this respect, it is similar to the large conductance channels (200-270 pS at symmetrical K + ) reported in many tissues (for reviews, see Latorre and Miller 33 and Tomita 31 ). In particular, it bears strong resemblance to the large-conductance K + channel of toad stomach cells 8 in terms of current density, external TEA, and Ca 2+ sensitivity.…”

Section: Time-independent K + Current I H Of Coronary Smooth Muscle supporting

confidence: 81%

“…Compared with other smooth muscle tissues (see Tomita 31 for reviews), whole-cell K + currents of the coronary smooth muscle cells are very large, with current density of 376.5 jiA/cm 2 . Such strikingly large current density has not been reported in other isolated smooth muscle cells except those of toad stomach measured with the two-microelectrode voltage-clamp technique.…”

Section: K + Channel Conductances In Coronary Smooth Muscle Cells Arementioning

confidence: 98%

See 1 more Smart Citation

Outward potassium currents in freshly isolated smooth muscle cell of dog coronary arteries.

Wilde

Lee

1989

Circulation Research

View full text Add to dashboard Cite

Outward membrane currents were characterized in single coronary smooth muscle cells of adult beagle dogs. The cells averaged 96.4 x 7.1 microns and had a resting potential of -50.7 mV, an input resistance of 307.9 M omega, a capacitance of 32.3 pF, and a calculated membrane surface area of 4,037 microns2. The cells contracted in response to external application of acetylcholine or high K+. In voltage clamp by use of the suction pipette method, outward current began to appear at -50 mV and reached 15.2 nA at 50 mV with a current density of 376.5 microA/cm2. The current was reduced by external tetraethylammonium, Ba2+, and internal Cs+, and its reversal potential had a Nernst relation to external K+ concentration. Elevation of external Ca2+ (Ca2+o) from 0 to 0.3 mM increased total K+ current by up to 300%; elevation of internal Ca2+ (Ca2+i) to 5 x 10(-7) M by internal perfusion increased total outward current to a similar extent, suggesting a large difference in Ca2+ transmembrane sensitivity. Total whole-cell K+ current consisted of two components: an initial time-independent current (Ii) followed by a time-dependent current (It). Ii and It were through separate K+ channels based on differences in a) sensitivity to Ca2+09b) modulation by an inward Ca2+ current, c) current amplitudes and activation kinetics, and d) responses to pharmacological agents. It was the largest component, measuring 4.5 nA in 0 mM Ca2+o but increasing to 11.9 nA in 0.3 mM Ca2+o with a steep 2.5 power function. It activated with a biexponential time course; in Ca2+o-free solution, its time course was relatively insensitive to voltage changes but became voltage sensitive in the presence of Ca2+o. Further, such sensitivity was abolished or enhanced by Co2+ or Bay K 8644, respectively. We concluded that there are two types of Ca2+-sensitive K+ currents, Ii and It, in coronary smooth muscle cells. Via an inward Ca2+ channel Ca2+o strongly modulates It, both in amplitude and kinetics.

show abstract

Section: Time-independent K + Current I H Of Coronary Smooth Muscle supporting

confidence: 81%

Section: K + Channel Conductances In Coronary Smooth Muscle Cells Arementioning

confidence: 98%

Outward potassium currents in freshly isolated smooth muscle cell of dog coronary arteries.

Wilde

Lee

1989

Circulation Research

View full text Add to dashboard Cite

show abstract

“…Recently, isolated single cells have proven to be useful to study electrical characteristics of the myometrium and other smooth muscle. With this procedure, several t pes of K t currents have been described with the Ca2+-activated K + current being recorded predominantly (Mollard et al, 1986;Okabe et al, 1987;Singer and Walsh, 1984;Terada et al, 198713;Tomita, 1988). Tor0 et al (1990b) characterized K + currents in isolated myometrial cells of adult rats, analyzed their occurrence in estrus and diestrus stages of the estrus cycle, and evaluated their possible regulation by norepinephrine.…”

Section: Nonpregnant State Potassium Channelsmentioning

confidence: 99%

Hormonal influence on ionic channels in myometrium

Ludmir

Erulkar

1993

Microscopy Res & Technique

View full text Add to dashboard Cite

Smooth muscle cells in culture isolated from myometrium were characterized by scanning microscope and immunohistochemistry. Using the whole-cell patch-clamp configuration, and the single channel bilayer technique, the properties of ionic channels expressed in both non-pregnant and pregnant myometrium have been described. The predominantly expressed potassium channel changes from a transient inactivating outward current seen before puberty, to a calcium sensitive delayed outward current present in the adult stage. A change in the calcium channel population occurs from the nonpregnant to the pregnant state. Finally, sodium channels are expressed with greater frequency towards the end of gestation suggesting that these channels may play a role in labor.

show abstract

“…Calcium activated potassium channels couple calcium metabolism and membrane potential to potassium flux and membrane excitability. Three types of calcium-dependent potassium channels have been described, such as large conductance, intermediate conductance and small conductance calcium-dependent potassium channels, and these can be separated by their single channel conductance, their voltage-dependence and their sensitivity to blockade by a variety of pharmacological agents (Tomita 1988). These channels are highly selective for potassium ions and are activated by small increases in the concentration of cytoplasmic calcium.…”

Section: Calcium-activated Potassium Channels (Kca)mentioning

confidence: 99%

“…The effect of increasing internal calcium concentration is considered mainly to increase the frequency of opening, i.e. to shorten the closed state and to prolong the open state (Tomita 1988). The channels are also voltage-gated and are activated by membrane depolarization.…”

Section: Calcium-activated Potassium Channels (Kca)mentioning

confidence: 99%

Cerebral Vascular Smooth Muscle Potassium Channels and their Possible Role in the Management of Vasospasm

Zhang

Cook

1994

Pharmacology & Toxicology

View full text Add to dashboard Cite

One of the promising therapeutic uses of the potassium channel openers is in the management of cerebral vasospasm, a prolonged vasoconstriction of major cerebral arteries which follows aneurysmal subarachnoid haemorrhage. In this review, we first summarize the properties of potassium channels in cerebral vascular smooth muscle. Calcium-activated and ATP-dependent potassium channels are the major potassium channels identified in the cerebrovascular smooth muscle and both are believed to play a role in the regulation of cerebrovascular smooth muscle tone. The calcium-activated potassium channels can be activated by depolarization, by elevation of internal calcium and by some vasodilators. Some neuropeptides and potassium channel openers open the ATP-dependent potassium channels and produce vasodilation. We then review the effects of both synthetic and endogenous potassium channel openers in the cerebrovascular system, discuss their efficacy in the management of models of cerebrovascular spasm, and outline the clinical promise of these agents.

show abstract

Ionic channels in smooth muscle studied with patch-clamp methods.

Cited by 33 publications

References 63 publications

Outward potassium currents in freshly isolated smooth muscle cell of dog coronary arteries.

Outward potassium currents in freshly isolated smooth muscle cell of dog coronary arteries.

Hormonal influence on ionic channels in myometrium

Cerebral Vascular Smooth Muscle Potassium Channels and their Possible Role in the Management of Vasospasm

Contact Info

Product

Resources

About