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

Wilde, Dixon W.; Lee, K S

doi:10.1161/01.res.65.6.1718

Cited by 32 publications

(18 citation statements)

References 30 publications

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“…Our records are consistent with pre- vious studies performed in guinea pigs, humans, rabbits (35), and rats (23). Most studies related to the characterization of membrane currents in coronary smooth muscle cells were performed on cells isolated from the LCA (8,21,26,35,37). In the present study, macroscopic outward currents were comparatively measured in myocytes from both LCA and RCA, and for the first time, we reported that macroscopic outward current elicited by membrane depolarization were greater in RCA cells than in LCA cells (Fig.…”

Section: Discussionsupporting

confidence: 89%

“…It is noteworthy that different types of K ϩ channels have been described in coronary myocytes from several animal models (8,22,23,35,37), supporting that coronary vascular tone may reflect the integrated contribution of a diverse population of K ϩ channels. Nevertheless, to the best of our knowledge no study has so far compared the contribution of the K ϩ channels in both LCA and RCA from the same species.…”

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confidence: 89%

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Heterogeneous Kv1 function and expression in coronary myocytes from right and left ventricles in rats

Gautier

Hyvelin²,

Crescenzo³

et al. 2007

American Journal of Physiology-Heart and Circulatory Physiology

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Gautier M, Hyvelin J-M, de Crescenzo V, Eder V, Bonnet P. Heterogeneous Kv1 function and expression in coronary myocytes from right and left ventricles in rats. Am J Physiol Heart Circ Physiol 292: H475-H482, 2007. First published May 26, 2006; doi:10.1152/ajpheart.00774.2005.-Coronary blood flow control is not uniform along the vascular tree and particularly between the right coronary artery and the left anterior descending artery. Resting membrane potential that contributes largely to the vascular tone is mainly regulated by K ϩ channels in coronary myocytes. In the present study, we hypothesized that right coronary artery (RCA) and left coronary artery (LCA) exhibited a cell-specific function of K ϩ channels. The net outward current was markedly greater in RCA compared with LCA cells, and this difference was due to a larger 4-aminopyridine (4-AP)-sensitive voltage-gated potssium (Kv) current in RCA cells, whereas the iberiotoxin (IbTx)-sensitive, large conductance Ca 2ϩ -dependent potassium (BK Ca) current was smaller in RCA cells. To go further in the molecular identity of this Kv current, we used 50 nM correolide, which specifically blocked Kv1 family ␣-subunits. Outward currents generated by ramp depolarization protocols were highly sensitive to correolide in both RCA and LCA cells, suggesting that Kv1 contributed for a large part to the net outward current. 4-APinduced contractions in isolated RCA, and LCA were greater than IbTx-induced contraction. Furthermore, the 4-AP-induced contraction in RCA was significantly greater than that in LCA, which is in agreement with the electrophysiological data. Finally, the Kv1.2 ␣-subunit but not the Kv1.5 was detected in both RCA and LCA using primary specific antibody in Western blotting and immunofluorescence assay, and expression of Kv1.2 ␣-subunit was markedly higher in RCA compared with LCA. In summary, we reported for the first time a heterogeneous function and expression of Kv1 ␣-subunits in rat coronary myocytes isolated from RCA or LCA. coronary circulation; potassium channel; perfused coronary; membrane currents THE FUNCTIONAL CHARACTERISTICS of the coronary circulation may be described in terms of the relationship between steadystate perfusion pressure and the amount of blood flow. There are functional hemodynamic differences among coronary vascular beds that are linked to pressure differences along the vascular bed. These differences in compressive forces result in almost continuous flow in the right coronary bed, whereas flow in the anterior left descending bed occurs mainly during diastole (24, 30). Furthermore, when aortic pressure rises and the ventricle is loaded, the right coronary bed exhibits reflex increase of blood flow, whereas the anterior left descending coronary artery vasodilates poorly (29). Such differences in the hemodynamic profile between the left (LCA) and right coronary arteries (RCA) may underline differences in the regulation of basal tone between these two vascular beds.The coronary vascular tone is modulated by several factors, ...

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Section: Discussionsupporting

confidence: 89%

mentioning

confidence: 89%

Heterogeneous Kv1 function and expression in coronary myocytes from right and left ventricles in rats

Gautier

Hyvelin²,

Crescenzo³

et al. 2007

American Journal of Physiology-Heart and Circulatory Physiology

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“…In these experiments, outward currents were elicited by a 600 msec voltage depolarizing step from -90 mV to +70 mV, followed by a 500 msec pulse to more "],,, these potentials were more positive than those predicted by the Nemst equation, 14 as has been noted previously. 15 However, the slopes of the plots were -58.5 (WKY), -56.2 (SHR), -56.5 (DS), and -54.3 (PS), similar to the slope of -5 8 predicted for a purely K + -selective channel by the Nernst equation.…”

Section: Comparison Of K + Currentssupporting

confidence: 68%

A Ca(2+)-dependent K+ current is enhanced in arterial membranes of hypertensive rats.

et al. 1992

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This study was designed to investigate the role and regulation of arterial membrane K + channels in hypertension. Aortic segments from normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were suspended for isometric tension recording. In other experiments, proximal aortic segments (PS) (exposed to high pressure) and distal aortic segments (DS) (exposed to lower pressure) were removed from surgically coarcted Sprague-Dawiey rats and similarly prepared. Aortas from SHR and PS dose-dependently contracted to the K + channel blocker tetraethylammonium (TEA) (0.1-10 mM), and this contraction was abolished by preincubation with 0.1 jtM nifedipine. In contrast, the same concentrations of TEA did not contract either WKY or DS aortas. Since block of K + channels by TEA had a different effect on aortic segments exposed to high versus low blood pressure, we compared whole-cell K + currents in isolated vascular cells from the same aortas. The reversal potentials of depolarizationinduced outward currents in WKY, SHR, DS, and PS aortic cells showed a Nernst relation to external K + concentration indicative of selective K + permeability. TEA (1 and 10 mM) was equipotent in blocking these K + currents in patch-clamped cells from all aortic preparations, suggesting that the lack of TEA-induced contractions in WKY and DS aortas was not due to an absence of TEA-sensitive K + channels in these arterial membranes. However, when the Ca 2+ ionophore A23187 (10 /iM) was used to increase the level of cytosolic Ca 2+ in patch-clamped cells, the K + current density in SHR and PS aortic cells was twofold or more higher than in WKY and DS cells. These data suggest that a Ca 2+ -activated, TEA-sensitive K + current is enhanced in aortic muscle cells exposed to high blood pressure. In the intact blood vessel, this may act as a compensatory mechanism to modulate the level of arterial contraction in hypertension. hypothesis that an increased K + permeability regulates arterial reactivity in genetic and experimental rat models of hypertension. In addition, patch-clamp experiments were performed to investigate the ionic channels and cellular mechanisms mediating the enhanced efflux. Our results suggest that a tetraethylammonium chloride (TEA)-sensitive, Ca 2+ -dependent K + current is increased in aortic muscle membranes from hypertensive rats. This K + current appears to be an important modulator of arterial contraction in arteries previously exposed to high blood pressure.Methods Adult (12-16 weeks) Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were obtained from Taconic Farms, Germantown, N.Y. On experimental days, blood pressure was measured by femoral catheterization during pentobarbital anesthesia (45 mg/kg i.p.). Mean arterial pressures (MAP) in WKY and SHR were 98±3 mm Hg and 140±5 mm Hg, respectively. In other experiments, Sprague-Dawiey rats (10 weeks) obtained from Sasco, Madison, Wis., were anesthetized with telazol (40 mg/kg i.m.), and the aorta was partially ligated between the renal art...

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“…Most other procedures employ mixtures of collagenase with other enzymes in Ca2"-free solutions (e.g. Bolton et al 1985;Inoue et al 1985;Wilde & Lee, 1989). The protocols are time consuming, taking up to 2 h and often requiring several incubations in enzyme.…”

Section: Cell Isolation Proceduresmentioning

confidence: 99%

“…However, the physiological relevance of this type of current is not yet clear. More recently, a quasiinstantaneous, time-independent K+ current has been reported in rabbit portal vein (Hume & Leblanc, 1989) and in dog coronary artery (Wilde & Lee, 1989), which might play a role in maintaining the resting membrane potential. This paper describes a new and convenient method for isolating cells and characterizes the major outward currents in rabbit pulmonary artery.…”

Section: Introductionmentioning

confidence: 99%

Outward currents in rabbit pulmonary artery cells dissociated with a new technique

Gurney¹

1991

Experimental Physiology

112

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SUMMARYSingle cells from the rabbit pulmonary artery were isolated using a new and convenient procedure. Strips of muscle were incubated overnight in papain at 6°C and dispersed the following morning after warming the tissue for 10 min. This method consistently produced a high yield of relaxed cells, which reversibly responded to vasoconstrictors and remained viable for many hours. The electrophysiological properties of these cells were studied using the patchclamp technique in the whole-cell configuration. In physiological Ca2+ solution with K+-filled pipettes, cells had a high input resistance (-17 GfQ) and an average resting potential of -55 mV. In voltage clamp, several components of outward current could be identified. Depolarizing voltage steps revealed a prominent, transient current (Iran), having extremely rapid activation (< S ms) and inactivation (< 15 ms) kinetics. 4ran was followed by a more slowly activating current ('KSO) that was sustained over 100 ms. Both currents were essentially abolished by a 4-aminopyridine (4-AP) and sensitive to Ca2+ influx. IKSO' but not Itran, was blocked by tetraethylammonium (TEA) and had the properties of a Ca2+-activated K+ current. Holding the membrane potential at -40 mV completely inactivated I4an and unmasked a timeindependent, background current superimposed on IKSO The background current was also blocked by 4-AP. In addition, when adenosine triphosphate (ATP), but not guanosine triphosphate (GTP), was omitted from the patch-pipette, spontaneous bursts of outward current (SOCs) were superimposed on the voltage-activated currents. However, since SOCs were rarely observed when ATP and GTP were present together, they are unlikely to be active under physiological conditions. Thus at least four types of outward current can be distinguished in isolated rabbit pulmonary artery cells. These include a novel transient current which could be activated from the resting potential. It activates much more rapidly than outward currents previously reported in vascular muscle, and would rapidly oppose action potential firing. This current could therefore be responsible for the inability of large elastic arteries to fire action potentials.

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

Cited by 32 publications

References 30 publications

Heterogeneous Kv1 function and expression in coronary myocytes from right and left ventricles in rats

Heterogeneous Kv1 function and expression in coronary myocytes from right and left ventricles in rats

A Ca(2+)-dependent K+ current is enhanced in arterial membranes of hypertensive rats.

Outward currents in rabbit pulmonary artery cells dissociated with a new technique

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