Single nonselective cation channels and Ca2+-activated K+ channels in aortic endothelial cells

Fichtner, H.; Fröbe, U.; Busse, Rudi; Kohlhardt, M.

doi:10.1007/bf01872125

Cited by 56 publications

(25 citation statements)

References 36 publications

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“…Half-maximal activation of the K+ channel and nonselective cation channel in inside-out patches occurred at a Ca2+ concentration of 6.5 ± 1.5 ,uM (mean ± SD; n = 3) and 7.8 ± 1.2 ,uM (n = 6), respectively. Electrophysiological properties were similar to those reported earlier for large conductance K+ channels (10,23) and nonselective cation channels in endothelial cells (24). (25) and membrane potential (26).…”

Section: Methodssupporting

confidence: 87%

Up-regulation of pressure-activated Ca(2+)-permeable cation channel in intact vascular endothelium of hypertensive rats.

Hoyer

Köhler

Haase

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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In endothelial cells, stretch-activated cation channels have been proposed to act as mechanosensors for changes in hemodynamic forces. We have identified a novel mechanosensitive pressure-activated channel in intact endothelium from rat aorta and mesenteric artery. The 18-pS cation channel responded with a multifold increase in channel activity when positive pressure was applied to the luminal cell surface with the patch pipette and inactivated at negative pipette pressure. Channel permeability ratio for K+, Na+, and Ca2+ ions was 1:0.98:0.23. Ca2+ influx through the channel was sufficient to activate a neighboring Ca2+-dependent K+ channel. Hemodynamic forces are chronically disturbed in arterial hypertension. Endothelial cell dysfunction has been implicated in the pathogenesis of arterial hypertension. In two comparative studies, density of the pressure-activated channel was found to be significantly higher in spontaneously hypertensive rats and renovascular hypertensive rats compared with their respective normotensive controls. Channel activity presumably leads to mechanosensitive Ca2+ influx and induces cell hyperpolarization by K+ channel activity. Both Ca2+ influx and hyperpolarization are known to induce a vasodilatory endothelial response by stimulating endothelial nitric oxide (NO) production. Up-regulation of channel density in hypertension could, therefore, represent a counterregulatory mechanism of vascular endothelium.

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Section: Methodssupporting

confidence: 87%

Up-regulation of pressure-activated Ca(2+)-permeable cation channel in intact vascular endothelium of hypertensive rats.

Hoyer

Köhler

Haase

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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“…In many preparations the depolarization was followed by pronounced oscillations in membrane potential. The ACh-evoked hyperpolarization reversed near the K+ reversal potential and was apparently evoked by activation of Ca2+-dependent K+ channels as suggested by others (ColdenStanfield et al 1987;Fichtner et al 1987). The ACh-evoked hyperpolarization was not blocked by TEA, but this compound has been reported to fail to block Ca2+-activated K+ channels in several cell types (Latorre, Oberhauser, Labarca & Alvarez, 1989).…”

Section: Acetylcholine-evoked Hyperpolarizationsupporting

confidence: 51%

Electrical properties of resting and acetylcholine‐stimulated endothelium in intact rat aorta.

Marchenko

Sage

1993

The Journal of Physiology

101

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SUMMARY1. The passive electrical properties and the effects of acetylcholine on the membrane potential of the endothelium of intact rat aorta were investigated using the whole cell mode of the patch clamp technique.2. Unstimulated endothelium had a membrane potential of -58 + 8 mV (S.E.M., n = 193; range -47 to -76 mV). The input resistance was 43 + 13 MQ (S.E.M., n = 8; range 26-64 MQ). KCl and BaCl2, but not tetraethylammonium (2 mM), 4-aminopyridine (5 mM) or 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS; 100 /M) depolarized the endothelium.3. Acetylcholine (0-2A4 gM) evoked in most preparations a biphasic response with a transient hyperpolarization to a value close to the K+ reversal potential, followed by depolarization beyond the resting potential. In 46 % of recordings, the depolarization was followed by oscillations in membrane potential. The duration of the hyperpolarization and magnitude of the depolarization was similar in all recordings from a given aorta, but varied greatly between different preparations.4. Hyperpolarization of the endothelium below the K+ reversal potential reversed the direction of the first phase of the acetylcholine-evoked response, which was unaffected by tetraethylammonium, 4-aminopyridine, or DIDS.5. The removal of extracellular Ca2+ evoked a depolarization of the endothelium from -61 + 3 to -34 + 3 mV (S.E.M., n = 9) over 2-15 min. Restoration of external Ca2+ evoked a transient hyperpolarization.6. ACh applied in nominally Ca2+-free medium shortly after Ca2+ removal evoked only a transient hyperpolarization. After the establishment of a stable membrane potential in Ca2+-free medium, acetylcholine was without effect. 7. NiCl2 (2 mM) evoked a small depolarization of the endothelium (6 + 2 mV; S.E.M., n = 7). The subsequent removal of Ni2+ evoked a transient hyperpolarization.8. In the presence of Ni2+, acetylcholine evoked a short-lived hyperpolarization. Both the application of Ni2+ and the removal of extracellular Ca2+ immediately blocked oscillations in membrane potential evoked by acetylcholine. S. M. MARCHENKO AND S. 0. SAGE membrane potential, depolarization of the endothelium alone, by current injection or application of KCl, did not evoke oscillations.11. The activator of protein kinase C, phorbol 12, 13-dibutyrate (200 nM) depolarized and greatly increased the input resistance of the endothelium, presumably due to an effect on gap junctions. The blockers of protein kinase C, staurosporine (200 nM) and H-7 (200 nM), were without effect on acetylcholineevoked responses.12. These results suggest that acetylcholine evokes complex changes in endothelial membrane potential following changes in cytosolic calcium concentration. The initial agonist-evoked hyperpolarization appeared dependent on the release of Ca2+ from intracellular stores, whilst the prolonged phase of the hyperpolarization, depolarization and oscillations in membrane potential are dependent upon the entry of Ca2+ through Ni2+-sensitive channels. Protein kinase C does not appear to be involved in...

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“…The openings of the NS channel are burst-like and exhibit complicated kinetics with at least two exponentials required to fit open time histograms and two or three exponentials required to fit closed time histograms. As with the nonselective channels reported in endothelial cells and mast cells (23,24), we are unable to demonstrate any direct correlation of channel open probability with internal calcium concentration (0.5 nM to 50 ,uM). In this respect, the NS channel differs from some nonselective channels (25)(26)(27).…”

Section: Resultsmentioning

confidence: 44%

“…NS channels have previously been demonstrated to respond in a tissue-specific fashion to a number of agonists (23,24,29,39,40). Although there has been no prior demonstration that NS channels play a role in growth factor response, other descriptions of serum (10) and epidermal growth factor (11) responses include loss of membrane potential ("depolarization phases" with reversal potential near 0 mV) and nonselective increase in membrane conductance (periods of ionic "leakiness").…”

Section: Discussionmentioning

confidence: 99%

Activation of single-channel currents in mouse fibroblasts by platelet-derived growth factor.

Frace¹,

Gargus²

1989

Proc. Natl. Acad. Sci. U.S.A.

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A nonselective cation channel that we characterized in the mouse L-cell membrane becomes quiescent with serum deprivation (arrested cell growth) and rapidly active upon readdition of serum or, specifically, plateletderived growth factor (PDGF). Using the patch-clamp technique, we find that the predominant channel in the LMTK-cell line is a bursting nonselective cation channel (the NS channel). In cell-attached and inside-out patches, the channel has a conductance of 28 pS; equal selectivity for Na+ We have attempted applications of several growth factors (fibroblast-derived growth factor, epidermal growth factor, insulin, bombesin, a-thrombin, and vasopressin, individually or in combination) but find that only PDGF (5-100 ng/ml; n = 9) produces channel activation. This activation should provide a Na+ entry pathway parallel to that of the Na/H exchanger.In a number of cell systems, changes in ion transport constitute an essential and rapid response to a variety of mitogenic growth factors (1). The best conserved and analyzed of the mechanisms underlying the rapid membrane response to growth factors are the nearly uniform activations of two cation carriers-the Na/H antiporter and the Na,KATPase (1-9). The stimulated Na/H antiporter increases intracellular pH and raises the intracellular Na+ concentration, effects that secondarily stimulate the Na/K pump and thereby raise the intracellular K+ concentration. In addition to these carriers, ion channels may form part of the rapid response mechanism to serum and growth factors. There are observations ofchanges in membrane potential (4, 10, 11) and a dependence on extracellular Ca2l for the increase in intracellular Ca2l (4,12) that follows the application of growth factors. The patch-clamp technique and the analysis of single-channel events allow the molecular definition of such channel mechanisms (13). These methods have already been used to clearly demonstrate the increased activity of a K+-selective channel and a Ca2+-selective channel in T lymphocytes in response to application of the mitogenic lectin phytohemagglutinin (14,15).We have investigated the effects of growth factors on the single-channel currents of the L-cell and have found that one specific channel becomes quiescent with serum deprivation and rapidly active upon readdition of serum or, specifically, platelet-derived growth factor (PDGF) in the mitogenic concentration range (5-10 ng/ml) (16). MATERIALS AND METHODSCells, Growth Factors, and Solutions. LMTK-is an established mouse fibroblast cell line (17) in which ion transport has been studied by a variety of physiological and genetic techniques (18-20). The cells were maintained in culture in a-MEM (GIBCO) supplemented with 5% horse serum (HyClone) and kept at subconfluent density throughout the experimental period. Cells for patch-clamp experiments were grown on glass coverslips and kept in 35-mm dishes for up to 2 days. Channel properties were assessed after transfer of a single coverslip to a small volume (200 pA) experimental chamber and e...

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Single nonselective cation channels and Ca2+-activated K+ channels in aortic endothelial cells

Cited by 56 publications

References 36 publications

Up-regulation of pressure-activated Ca(2+)-permeable cation channel in intact vascular endothelium of hypertensive rats.

Up-regulation of pressure-activated Ca(2+)-permeable cation channel in intact vascular endothelium of hypertensive rats.

Electrical properties of resting and acetylcholine‐stimulated endothelium in intact rat aorta.

Activation of single-channel currents in mouse fibroblasts by platelet-derived growth factor.

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