Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Patch clamp  (15)
  • Carbachol  (11)
  • CFTR  (9)
  • Cystic fibrosis  (8)
  • Rat  (7)
Source
Material
Years
Keywords
  • 11
    Electronic Resource
    Electronic Resource
    Effect of intracellular pH on agonist-induced [Ca2+]i transients in HT29 cells (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 466-474 
    Details
    ISSN: 1432-2013
    Keywords: Key words BCECF ; Fura-2 ; pHi ; [Ca2+]i ; HT29 ; Carbachol ; Neurotensin ; ATP ; InsP3 ; Cell volume ; Calcein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In this study we examined the influence of intracellular pH (pHi) on agonist-induced changes of intracellular Ca2+ activity ([Ca2+]i) in HT29 cells. pHi and [Ca2+]i were measured microspectrofluorimetrically using BCECF and fura-2, respectively. Buffers containing trimethylamine (TriMA), NH3/NH4 + and acetate were used to clamp pHi to defined values. The magnitudes of the peak and plateau of [Ca2+]i transients induced by carbachol (CCH, 10–6 mol/l) were greatly enhanced by an acidic pHi and nearly abolished by an alkaline pHi. The relationship between pHi and the [Ca2+]i peak was nearly linear from pHi 7.0 to 7.8. This effect of pHi was also observed at higher CCH concentrations (10–4 and 10–5 mol/l), at which the inhibitory effect of an alkaline pHi was more pronounced than the stimulatory effect of an acidic pHi. An acidic pHi shifted the CCH concentration/response curve to the left, whereas an alkaline pHi led to a rightward shift. The influence of pHi on [Ca2+]i transients induced by neurotensin (10–8 mol/l) or ATP (5 × 10–7 mol/l) was similar to its influence on those induced by CCH, but generally not as pronounced. Measurements of cellular inositol 1,4,5-trisphosphate (InsP 3) showed no changes in response to acidification with acetate (20 mmol/l) or alkalinization with TriMA (20 mmol/l). The InsP 3 increase induced by CCH was unaltered at an acidic pHi, but was augmented at an alkaline pHi. Confocal measurements of cell volume showed no significant changes induced by TriMA or acetate. Slow-whole-cell patch-clamp experiments showed no additional effect of CCH on the membrane voltage (V m) measured after TriMA or acetate application. We conclude that pHi is a physiological modulator of hormonal effects in HT29 cells, as the [Ca2+]i responses to agonists were significantly changed at already slightly altered pHi. The measurements of InsP 3, cell volume and V m show that pHi must act distally to the InsP 3 production, and not via changes of cell volume or V m.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050422
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Potassium conductance of smooth muscle cells from rabbit aorta in primary culture (1991)
    Springer
    Pflügers Archiv 419 (1991), S. 57-68 
    Details
    ISSN: 1432-2013
    Keywords: Vascular smooth muscle cell ; K+ conductance ; Big Ca2+-dependent K+ channel ; Patch clamp ; Verapamil ; Protein kinase C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Vascular smooth muscle cells were obtained from rabbit aorta and were studied in primary culture on days 1–7 after seeding with electrophysiological techniques. In impalement experiments a mean membrane potential difference (PD) of −50±0.3 mV (n=387) was obtained with Ringer-type solution in the bath. PD was depolarized by 6±0.3 mV (n=45) and 16±2 mV (n= 5) when the bath K+ concentration was increased from the control value of 3.6 mmol/l to 13.6 and 23.6 mmol/l, respectively. Ba2+ (0.1–1 mmol/l) depolarized PD. Tetraethylammonium (TEA, 10 mmol/l) depolarized PD only slightly but significantly. Verapamil (0.1 mmol/l) and charybdotoxin (10 nmol/l) had no effect on PD. The conductance properties of these cells were further examined with the patch-clamp technique. K+ channels were spontaneously present in cell-attached patches. When the pipette was filled with 145 mmol/l KCl, a mean conductance (g K) of 209.6±4.6 mV (n=17) was read from the current/voltage curves at a clamp voltage (V c) of 0 mV. After excision K+ channels were found in 129 patches with inside-out and in 50 with outside-out configuration. With KCl on one and NaCl on the other side the mean g K at a V c of 0 mV was 134.6±3.9 pS (n=179). The mean permeability was 0.89±0.03×10−12 cm3/s. With symmetrical KCl solution the mean g K was 227±6 pS (n=17). The conductance sequence was g K≫ g Rb= g Cs=g Na=0. TEA blocked dose-dependently only from the outside.(1–10 mmol/l). Lidocaine (5 mmol/l) quinidine (0.01–1 mmol/l) and quinine (0.01–1 mmol/l) blocked from both sides. Charybdotoxin (0.5–5 nmol/l) blocked only from the extracellular side. Ba2+ blocked from the cytosolic side and the inhibition was increased by depolarization and reduced by hyperpolarization. At a V c of 0 mV a half-maximal inhibition (IC50) of 2 μmol/l was obtained. Verapamil and diltiazem blocked from both sides, verapamil with an IC50 of 2 μmol/l and diltiazem with an IC50 of 10 μmol/l. The open probability of this channel was increased by Ca2+ on the cytosolic side at activities 〉 0.1 μmol/l. Half-maximal activation occurred at Ca2+ activities exceeding 1 μmol/l. The present data indicate that the vascular smooth muscle cells of rabbit aorta in primary culture possess a K+ conductance. In excised patches only a maxi K+ channel was detected. This channel has properties different from the macroscopic K+ conductance. Hence, it is likely that the K+ conductance of the intact cell is dominated by yet another and thus far not detected K+ channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373748
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Cation specificity and pharmacological properties of the Ca2+-dependent K+ channel of rat cortical collecting ducts (1993)
    Springer
    Pflügers Archiv 422 (1993), S. 481-491 
    Details
    ISSN: 1432-2013
    Keywords: Patch clamp ; Verapamil ; Charyb-dotoxin ; Apamin ; K+ channel blocker ; Permselectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The luminal membrane of principal cells of rat cortical collecting duct (CCD) is dominated by a K+ conductance. Two different K+ channels are described for this membrane. K+ secretion probably occurs via a small-conductance Ca2+-independent channel. The function of the second, large-conductance Ca2+-dependent channel is unclear. This study examines properties of this channel to allow a comparison of this K+ channel with the macroscopic K+ conductance of the CCD and with similar K+ channels from other preparations. The channel is poorly active on the cell. It has a conductance of 263±11 pS (n=36, symmetrical K+ concentrations) and of 139±3 pS (n=91) with 145 mmol/l K+ on one side and 3.6 mmol/l K+ on the other side of the membrane. Its open probability is high after excision (0.71±0.03, n=85). The channel flickers rapidly between open and closed states. Its permeability in the cell-free configuration was 7.0±0.2×10−13 cm3/s (n=85). It is inhibited by several typical blockers of K+ channels such as Ba2+, tetraethylammonium, quinine, and quinidine and high concentrations of Mg2+. The Ca2+ antagonists verapamil and diltiazem also inhibit this K+ channel. As is typical for the maxi K+ channel, it is inhibited by charybdotoxin but not by apamin. The selectivity of this large-conductance K+ channel demonstrates significant differences between the permeability sequence (P K 〉 P Rb 〉 P NH4 〉 P Cs=P Li=P Na=P choline=0) and the conductance sequence (g K 〉 g NH4 〉 g Rb 〉 g Li=g choline 〉 g Cs=g Na=0). The only other cations that are significantly conducted by this channel besides K+ (g K at V c =∞ is 279±8 pS, n=88) are NH 4 + (g NH4=127±22 pS, n=10) and Rb+ (g Rb=36±5 pS, n=6). The K+ currents through this channel are reduced by high concentrations of choline+, Cs+, Rb+, and NH 4 + . These properties and the dependence of this channel on Ca2+ and voltage classify it as a “maxi” K+ channel. A possible physiological function of this channel is discussed in the accompanying paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375076
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    The ion conductances of colonic crypts from dexamethasone-treated rats (1996)
    Springer
    Pflügers Archiv 431 (1996), S. 419-426 
    Details
    ISSN: 1432-2013
    Keywords: Key words Colon ; Triamterene ; Amiloride ; Na+ channel ; Cl ; channel ; K+ channel ; Carbachol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Whole-cell patch-clamp studies were performed in isolated colonic crypts of rats pretreated with dexamethasone (6 mg/kg subcutaneously on 3 days consecutively prior to the experiment). The cells were divided into three categories according to their position along the crypt axis: surface cells (s.c.); mid-crypt cells (m.c.) and crypt base cells (b.c.). The zero-current membrane voltage (V m) was −56 ± 2 mV in s.c (n = 34); −76 ± 2 mV in m.c. (n = 47); and −87 ± 1 mV in b.c. (n = 87). The whole-cell conductance (G m) was similar (8–12 nS) in all three types of cells. A fractional K+ conductance accounting for 29–67% of G m was present in all cell types. A Na+ conductance was demonstrable in s.c. by the hyperpolarizing effect on V m of a low-Na+ (5 mmol/l) solution. In m.c. and b.c. the hyperpolarizing effect was much smaller, albeit significant. Amiloride had a concentration-dependent hyperpolarizing effect on V m in m.c. and even more so in s.c.. It reduced G m by approximately 12%. The dissociation constant (K D) was around 0.2 μmol/l. Triamterene had a comparable but not additive effect (K D = 30 μmol/l, n = 14). Forskolin (10 μmol/l, in order to enhance cytosolic adenosine 3′, 5′-cyclic monophosphate or cAMP) depolarized V m in all three types of cells. The strongest effect was seen in b.c.. G m was enhanced significantly in b.c. by 83% (forskolin) to 121% [8-(4-chlorophenylthio)cAMP]. The depolarization of V m and increase in G m was caused to large extent by an increase in Cl−conductance as shown by the effect of a reduction in bath Cl−concentration from 145 to 32 mmol/l. This manoeuvre hyperpolarized V m under control conditions significantly by 6–9 mV in all three types of cells, whilst it depolarized V m in the presence of forskolin in m.c. and in b.c.. These data indicate that s.c. of dexamethasone-treated rats possess mostly a K+ conductance and an amiloride- and triamterene-inhibitable Na+ conductance. m.c. and b.c. possess little or no Na+ conductance; their V m is largely determined by a K+ conductance. Forskolin (via cAMP) augments the Cl− conductance of m.c. and b.c. but has only a slight effect on s.c.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02207281
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Evidence for agonist-induced export of intracellular Ca2+ in epithelial cells (1993)
    Springer
    Pflügers Archiv 424 (1993), S. 423-430 
    Details
    ISSN: 1432-2013
    Keywords: [Ca2+]i export ; Thapsigargin ; fura-2 ; HT29 ; CFPAC-1 ; ATP ; Carbachol ; Neurotensin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There is increasing evidence that some agonists not only induce intracellular Ca2+ increases, due to store release and transmembranous influx, but also that they stimulate Ca2+ efflux. We have investigated the agonist-stimulated response on the intracellular Ca2+ activity ([Ca2+]i) in the presence of thapsigargin (10−8 mol/l, TG) in HT29 and CFPAC-1 cells. For CFPAC-1 the agonists ATP (10−7–10−3 mol/l, n=9), carbachol (10−6–10−3 mol/l, n=5) and neurotensin (10−10–10−7 mol/l, n=6) all induced a concentration-dependent decrease in [Ca2+]i in the presence of TG. Similar results were obtained with HT29 cells. This decrease of [Ca2+]i could be caused by a reduced Ca2+ influx, either due to a reduced driving force for Ca2+ in the presence of depolarizing agonists or due to agonist-regulated decrease in Ca2+ permeability. Using the fura-2 Mn2+ quenching technique we demonstrated that ATP did not slow the TG-induced Mn2+ quench. This indicates that the agonist-induced [Ca2+]i decrease in the presence of TG was not due to a reduced influx of Ca2+ into the cell, but rather due to stimulation of Ca2+ export. We used the cell attached nystatin patch clamp technique in CFPAC-1 cells to examine whether, in the presence of TG, the above agonists still led to the previously described electrical changes. The cells had a mean membrane voltage of −49±3.6 mV (n=9). Within the first 3 min ATP was still able to induce a depolarization which could be attributed to an increase in Cl− conductance. This was expected, since at this time after TG stimulation all Ca2+ agonists still liberated some [Ca2+]i. When TG incubation was prolonged, agonist application led to strongly attenuated or to no electrical responses. Therefore, the agonist-stimulated [Ca2+]i decrease cannot be explained by the reduction of the driving force for Ca2+ into the cell. In the same cells hypotonic swelling (160 mosmol/l, n=15) still induced a further [Ca2+]i increase in the presence of TG and concomitantly induced Cl− and K+ conductances. We conclude that the agonist-induced decrease of [Ca2+]i in the presence of TG probably unmasks a stimulation of [Ca2+]i export.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374904
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Small and intermediate conductance chloride channels in HT29 cells (1993)
    Springer
    Pflügers Archiv 424 (1993), S. 456-464 
    Details
    ISSN: 1432-2013
    Keywords: Cl− channels ; Cl− secretion ; HT29 ; Ca2+ ; cAMP ; Protein kinase A ; Cytosolic inhibitor ; Cystic fibrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recently, it has been shown that intermediate conductance outwardly rectifying chloride channels (ICOR) are blocked by cytosolic inhibitor (C. I.) found in the cytosol of human placenta and epithelial cells. C. I. also reduced the baseline current in excised membrane patches of HT29 cells. In the present study, this effect of C. I. was characterized further. Heat treated human placental cytosol was extracted in organic solvents and dissolved in different electrolyte solutions. It is shown that the reduction of baseline conductance (g o) is caused by inhibition of small non-resolvable channels, which are impermeable to Na+ and SO4 2−, but permeable to Cl−. The regulation of these small Cl−-conducting channels (g o) and of ICOR was examined further. First, no activating effects of protein kinase A (PKA) on the open probability (P o) of the ICOR or on the go) were observed. The Po of the ICOR was reduced by 22% in a Ca2+-free solution. g o was insensitive to changes in the Ca2+ activity. The effects of C. I. from a cystic fibrosis (CF) placenta and the CF pancreatic duct cell line CFPAC-1 were compared with the effects of corresponding control cytosols, and no significant differences between CF and control cytosols were found. We conclude that the excised patches of HT29 cells contain ICOR and small non-resolvable Cl−-conducting channels which are similarly inhibited by C. I. Apart from a weak effect of Ca2+ on the ICOR, g o and the ICOR do not seem to be directly controlled by Ca2+ or PKA. C. I. of normal and CF epithelia have a similar inhibitory potency on Cl− channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374908
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    cAMP stimulation of CFTR-expressing Xenopus oocytes activates a chromanol-inhibitable K+ conductance (1996)
    Springer
    Pflügers Archiv 432 (1996), S. 516-522 
    Details
    ISSN: 1432-2013
    Keywords: Key words Cl ; channel ; K+ channel ; Cellular homeostasis ; Cystic fibrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Cystic fibrosis transmembrane conductance regulator (CFTR) functions as a Cl–channel in a large variety of cells expressing this protein. Recently evidence has accumulated that it also regulates other ion channels. A coordinated increase in Cl–and K+ conductances is necessary in many Cl–-secreting epithelia. This has, for example, recently been demonstrated for the colonic crypt, for which a new type of K+ channel and a specific inhibitor of this channel, the chromanol 293B, have been described. In the present study we have examined whether the cAMP-evoked activation of CFTR, overexpressed in Xenopus oocytes, in addition to its known activation of a Cl–conductance, also upregulates endogenous K+ channels. It is shown that CFTR-cRNA-injected but not water-injected oocytes possess a cAMP-activated Cl–conductance. Of the cAMP-induced whole-cell current increase, 15–25% was due to a 293B-, Ba2+and TEA+-inhibitable K+ conductance. The cRNA of the mutated CFTR (ΔF508 CFTR) had no such effect. We conclude that cAMP activated CFTR and an endogenous IsK-type and 293B-sensitive K+ conductance. Similar events, occurring, for example, in the colonic crypt possessing CFTR and 293B-sensitive K+ channels, might explain the coordinated cAMP-mediated increase in Cl–and K+ conductances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050164
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Na+ and Cl− conductances in airway epithelial cells: increased Na+ conductance in cystic fibrosis (1995)
    Springer
    Pflügers Archiv 431 (1995), S. 1-9 
    Details
    ISSN: 1432-2013
    Keywords: Na+ channel ; Respiratory epithelial cells ; Human Na+ channel ; Micropuncture ; Patch clamp ; Cystic fibrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Na+ and Cl− conductances in the apical membrane of respiratory epithelial cells are essential for electrolyte and water transport in the airways. Apart from the well described defect in adenosine 3′∶5′ cyclic monophosphate-(cAMP-) dependent activation of Cl− conductances in cystic fibrosis (CF), an increased Na+ conductance has also been reported from transepithelial measurements. In the present experiments we tried to identify these conductances in nasal epithelial cells using patch-clamp and microelectrode techniques. With these methods we found identical and relatively low membrane voltages of about −36 mV in both freshly isolated and primary cultured normal and CF nasal epithelial cells. A Cl− conductance could be activated by cAMP in normal (ΔG=3.1±0.8 nS, n=10) but not in CF (ΔG=0.3±0.1 nS, n=11) cells, whereas Ca2+-dependent Cl− currents activated by adenosine 5′-triphosphate (ATP) and bradykinin were present in both types of cells. Cell-attached membrane patches from stimulated cells did not reveal discernible singlechannel events when activated with any of the agonists. A Na+ conductance was also detected in freshly isolated ciliated respiratory cells in impalement studies, as evidenced by the hyperpolarization induced by 10 μmol/l amiloride (ΔV= −5.2±0.6 mV, n=56) and when Na+ was replaced in the bath by N-methyld-glucamine (NMDG) (ΔV = −5.7±0.9 mV, n=14). In whole-cell patch-clamp experiments, the amilorideinduced hyperpolarization was significantly larger in CF (ΔV = −9.7±2.4 mV, n=22) when compared to normal (ΔV = −3.3±0.9 mV, n=27) cells in short-term culture. Reverse transcriptase polymerase chain reaction analysis of normal respiratory cells identified messenger RNA of both the cystic fibrosis transmembrane conductance regulator (CFTR) as well as the human epithelial Na+ channel (hNaCh). The present experiments confirm the absence of a cAMP-dependent Cl− conductance in CF respiratory epithelial cells and support previous findings obtained in transepithelial and microelectrode studies which indicate an increased Na+ conductance in respiratory epithelial cells from CF patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374371
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    N-Acetyl-l-cysteine and its derivatives activate a Cl− conductance in epithelial cells (1996)
    Springer
    Pflügers Archiv 431 (1996), S. 549-555 
    Details
    ISSN: 1432-2013
    Keywords: N-Acetyl-l-cysteine-S-Carboxymethyl-l-cysteine ; Respiratory epithelial cells ; Cystic fibrosis ; CFTR ; Cl− conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract N-Acetyl-l-cysteine (NAC) is a widely used mucolytic drug in patients with a variety of respiratory disorders including cystic fibrosis (CF). The beneficial effects of NAC are empirical and the exact mechanism of action in the airways remains obscure. In the present study we examined the effects on whole-cell (we) conductance (G m) and voltage (V m) of NAC and the congeners S-carboxymethyl-l-cysteine (CMC) andS-carbamyl-L-cysteine (CAC) andL-cysteine in normal and CF airway epithelial cells.L-Cysteine (1 mmol/1) had no detectable effect. The increase inG m (ΔGm) by the other compounds was concentration dependent and was (all substances at 1 mmol/1) 3.8 ± 1.4 nS (NAC; n = 11), 4.2 ± 1.0 nS (CMC;n = 16) and 3.8 ± 1.6 nS (CAC;n = 18), respectively. The changes in Gm were paralleled by an increased depolarization (ΔVm) when extracellular Cl− concentration was reduced to 34 mmol/1: under control conditions = -4.1 ± 2.1 versus 10.2 ± 2.1 mV in the presence of NAC, CMC, CAC (n = 36). In the presence of NAC, CMC and CAC, the reduction in Cl− concentration was paralleled by a reduction ofG m by 2.1 ± 0.4 nS (n = 35), indicating that all substances acted by increasing the Cl− conductance. Analysis of intracellular pH did not reveal any changes by any of the compounds (1 mmol/1). A Cl− conductance was also activated in HT29 colonic carcinoma and CF tracheal epithelial (CFDE) cells but not in CFPA1 cells, which do not express detectable levels of ΔF508-CFTR, suggesting that the presence of CFTR may be a prerequisite for the induction of Cl− currents. Next we examined the ion currents in Xenopus oocytes microinjected with CFTR-cRNA. Water-injected oocytes did not respond to activation by forskolin and 3-isobutyl-l-methylxanthine (IBMX) (ΔGm = 0.08 ±0.04 μS;n = 10) and no current was activated when these oocytes were exposed to NAC or CMC. In contrast, in CFTR-cRNA-injected cocytesG m was enhanced when intracellular adenosine 3′,5′-cyclic monophosphate (cAMP) was increased by forskolin and IBMX (G m = 4.5 ± 1.3 μS;n = 8).G m was significantly increased by 0.74 ± 0.2 μS (n = 11) and 0.46 ± 0.1 μS (n = 10) when oocytes were exposed to NAC and CMC, respectively (both I mmol/1). In conclusion, NAC and its congeners activate Cl− conductances in normal and CF airway epithelial cells and hence induce electrolyte secretion which may be beneficial in CF patients. CFTR appears to be required for this response in an as yet unknown fashion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02191902
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Culture-dependent expression of Na+ conductances in airway epithelial cells (1996)
    Springer
    Pflügers Archiv 431 (1996), S. 578-586 
    Details
    ISSN: 1432-2013
    Keywords: αhENaC ; Airway epithelial cells Amiloride ; CFTR ; Patch clamp ; RT-PCR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract According t0 previous studies, amiloride-sensitive (Amil+) Na+ channels are present in apical membranes of airway epithelial cells. When isolated from intact tissue and grown in primary culture 0r as immortalized cell lines, these cells tend t0 lose these Amil+ Na+ channels. The present study examines this issue in immortalized human bronchial epithelial cells (16HBE140- cell line). The mRNA of one subunit of the Na+ channel (αhENaC) was semi-quantified by polymerase chain reaction of reverse transcribed RNA. Transcripts were significantly increased when cells were exposed t0 aldosterone and dexamethasone irrespective of whether grown on permeable supports 0r plastic. When grown on plastic dishes 16HBE140-cells showed cAMP-dependent Cl− currents in whole-cell (WC) patch-clamp experiments, corresponding t0 expression of the cystic fibrosis transmembrane conductance regulator (CFTR). Na+ currents could not be detected although cells expressed significant amounts ofαhENaC as demonstrated by Northern blot analysis. In contrast, when cells were grown on permeable supports 0r cultured in the presence of butyrate (5 mmol/l, plastic 0r permeable support) 0r aldosterone and dexamethasone (both 1 μol/l, plastic 0r permeable support), amiloride (10 μmol/1) hyperpolarized the membrane voltage (ΔVm) by 2–9 mV paralleled by small reductions of WC conductances (ΔGm) of 0.4-4.0 nS. The effects of amiloride on ΔVm were generally more pronounced (up t0 12 mV) when cells were grown on permeable supports. The amiloride effect (ΔVm) was concentration dependent with an inhibitory constant, Ki, of about 0.1 μmol/l. We further examined whether the induction of an Amil+ Na+ conductance was paralleled by additional changes in membrane conductance. In fact, the cAMP-activated Cl− conductance was significantly attenuated by approximately 80% (n = 35) in cells responding t0 amiloride, whilst the ATP-activated K+ conductance remained unaffected. The present data suggest that cellular mechanisms determining differentiation control the functional expression of Na+ and Cl− conductances in human airway epithelial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02191906
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...