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  • Cl− conductance  (11)
  • Rat  (7)
  • 11
    Electronic Resource
    Electronic Resource
    Ca2+- and swelling-induced activation of ion conductances in bronchial epithelial cells (1994)
    Springer
    Pflügers Archiv 428 (1994), S. 597-603 
    Details
    ISSN: 1432-2013
    Keywords: Cl− conductance ; K+ conductance ; ATP ; Bradykinin ; Histamine ; Bronchial epithelial cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study was performed to examine Ca2+-dependent and cell-swelling-induced ion conductances in a polarized bronchial epithelial cell line (16HBE14o-). Whole-cell currents were measured in fast and slow whole-cell patch-clamp experiments in cells grown either on filters or on coated plastic dishes. In addition the transepithelial voltage (V te) and resistance (R te) were measured in confluent monolayers. Resting cells had a membrane voltage (V m) of −36±1.1 mV (n=137) which was mainly caused by K+ and Cl− conductances and to a lesser extent by a Na+ conductance. V te was apical-side-negative after stimulation. Equivalent short-circuit current (I sc = V te/R te) was increased by the secretagogues histamine (0.1 mmol/l), bradykinin (0.1–10 μmol/l) and ATP (0.1–100 μmol/l). The histamine-induced I sc was blocked by either basolateral diphenhydramine (0.1 mmol/l, n=4) or apical cimetidine (0.1 mmol/l, n=4). In fast and slow whole-cell recordings ATP and bradykinin primarily activated a transient K+ conductance and hyperpolarized V m. This effect was mimicked by the Ca2+ ionophore ionomycin (1 μmol/l, n=11). Inhibition of the bradykinin-induced I sc by the blocker HOE140 (1 μmol/l, n=3) suggested the presence of a BK2 receptor. The potency sequence of different nucleotide agonists on the purinergic receptor was UTP ≈ ATP 〉 ITP 〉 GTP ≈ CTP ≈ [β,γ-methylene] ATP ≈ 2-methylthio-ATP = 0 and was obtained in I sc measurements and patch-clamp recordings. This suggests the presence of a P2u receptor. Hypotonic cell swelling activated both Cl− and K+ conductances. The Cl− conductance was only slightly inhibited by 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (0.5 mmol/ l, n=3). These data indicate that 16HBE140- bronchial epithelial cells, which are known to express high levels of cystic fibrosis transmembrane conductance regulator protein, form a secretory epithelium. While hypotonic cell swelling activates both K+ and Cl− channels, the Ca2+-induced Cl− secretion is due mainly to activation of basolateral K+ channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374583
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  • 12
    Electronic Resource
    Electronic Resource
    Ion conductances of isolated cortical collecting duct cells (1992)
    Springer
    Pflügers Archiv 421 (1992), S. 381-387 
    Details
    ISSN: 1432-2013
    Keywords: Rat ; Cell isolation ; K+ channels ; Na+-conductance ; Patch clamp ; Cell-attached-nystatin technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The study of ion conductances in the intact cortical collecting duct (CCD) with the patch-clamp method is rather difficult. An optimized method to isolate CCD cells from rat kidneys using an in vivo followed by an in vitro enzyme digestion is described. Individual CCD segments were collected after this digestion and incubated in EGTA-buffered medium. This procedure resulted in single cells or cell clusters. These freshly isolated CCD cells were studied with different modifications of the patch-clamp method. Membrane voltages measured in the cell-attached-nystatin configuration were −74 ±1mV (n=13) and −68±3 mV (n=22) in cells isolated from normal and mineralocorticoid-treated rats respectively. These values and those measured with the nystatin-perforated slow-whole-cell configuration (−79 ±1mV, n=23) are comparable to those measured in principal cells of isolated CCD segments. The cells hyperpolarized after the addition of amiloride and depolarized with the addition of adiuretin to the bath. The amiloride effect was enhanced when cells were isolated from deoxycorticosterone-acetate-treated rats. The cells were strongly depolarized upon elevation of the extracellular K+-concentration and did not demonstrate a measurable Cl− conductance. A large-conductance K+ channel (174 pS, n=5, cell-attached, 145 mmol/l K+ in the pipette; 140 pS, n=12, cell-free, 3.6 mmol/l K+ in the bath) was seen. It had a very low activity on the cell, but a high open probability when excised into a solution with 1 mmol/l Ca2+ on the cytosolic side. More often a small-conductance K+ channel (36–52 pS, n=19, cell-attached; 30 pS, n=5, cell-free) with a high open probability was found on the cell. These freshly isolated cells seem to be a powerful preparation to study the properties and regulation of ion conductances of rat CCD with several electrophysiological methods. These freshly isolated CCD cells maintain the conductance properties known from principal cells of the intact CCD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374227
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  • 13
    Electronic Resource
    Electronic Resource
    Effect of bradykinin and histamine on the membrane voltage, ion conductances and ion channels of human glomerular epithelial cells (hGEC) in culture (1993)
    Springer
    Pflügers Archiv 424 (1993), S. 137-144 
    Details
    ISSN: 1432-2013
    Keywords: Human glomerular epithelial cells ; Bradykinin ; Histamine ; Nystatin patch clamp technique ; K+ conductance ; Maxi K+ channel ; Cl− conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of bradykinin (BK) and histamine (Hist) on the membrane voltage (V m), ion conductances and ion channels of cultured human glomerular epithelial cells (hGEC) were examined with the nystatin patch clamp technique. Cells were studied between passage 3 and 20 in a bath rinsed with Ringer-like solution at 37°C. The mean value of V m was −41±0.5 mV (n=189). BK (10−6 mol/l, n=29) and Hist (10−5 mol/l, n= 55) induced a rapid transient hyperpolarization by 15±1 mV and 18±1 mV, respectively. The hyperpolarization was followed by a long lasting depolarization by 6±1 mV (BK 10−6 mol/l) and 7±1 mV (Hist 10−5 mol/l). The ED50 was about 5×10−8 mol/l for BK and 5×10−7 mol/l for Hist. In the presence of both agonists, increases of outward and inward currents were observed. A change in the extracellular K+ concentration from 3.6 to 30 mmol/l depolarized V m by 8±1 mV and completely inhibited the hyperpolarizing effect of both agents (n=11). Reduction of extracellular Cl− concentration from 145 to 30 mmol/l led to a depolarization by 2 ±1 mV (n=25). In 30 mmol/l Cl− the depolarizations induced by BK (10−7 mol/l) and Hist (10−6 mol/l) were augmented to 9±2 mV (n=14) and to 10±2 mV (n=11), respectively. Ba2+ (5 mmol/l) depolarized V m by 19±5 mV (n=6) and completely inhibited the hyperpolarization induced by BK (10−6 mol/l, n=3) and reduced that of Hist (10−5 mol/l) markedly (n=3). Preincubation with the K+ channel blocker charybdotoxin (1–10 nmol/l) for 3 min had no significant effect on V m, but reduced markedly the BK(10−6 mol/l, n=11) and Hist-(10−5 mol/l, n=6) induced hyperpolarizations. In 10 out of 31 experiments in the cell attached nystatin patch configuration big K+ channels with a conductance $$(g_{K^ + } )$$ of 247±17 pS were found. The open probability of these K+ channels was increased 3- to 5-fold during the hyperpolarization induced by BK (10−7 mol/l) or Hist (10−5 mol/l, both n= 4). In excised inside/out patches this K+ channel had a mean conductance of 136±8.5 pS (n=10, clamp voltage 0 mV). The channel was outwardly rectifying and its open probability was increased when Ca2+ on the cytosolic side was greater than 0.1 μmol/l. The data indicate that BK and Hist activate a $$(g_{K^ + } )$$ and a $$g_{Cl^ - } $$ in hGEC. The hyperpolarization is induced by the activation of a Ca2+-dependent maxi K+ channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374604
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  • 14
    Electronic Resource
    Electronic Resource
    The effect of secretagogues on ion conductances of in vitro perfused, isolated rabbit colonic crypts (1995)
    Springer
    Pflügers Archiv 429 (1995), S. 494-502 
    Details
    ISSN: 1432-2013
    Keywords: Cl− secretion ; cAMP ; K+ conductance ; Cl− conductance ; Diarrhoea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Several secretagogues were used in this study, including those which enhance intracellular cyclic adenosine monophosphate (cAMP) production, as well as others which elevate intracellular Ca2+ activity and are known to increase Cl− secretion in the intact colon and in colonic carcinoma cell lines. They were examined with respect to their effects on electrophysiological properties in isolated rabbit distal colonic crypts. Crypts were dissected manually and perfused in vitro. Transepithelial voltage (V te), transepithelial resistance (R te), membrane voltage across the basolateral membrane (V bl), and fractional basolateral membrane resistance (FR bl), were estimated. Basolateral prostaglandin E2 (PGE2, ⩾0.1 μmol/l), vasoactive intestinal peptide (VIP, 1 nmol/l) and adenosine (0.1 mmol/l) induced an initial depolarisation and a secondary partial repolarisation of (V bl). In the case of adenosine, the initial depolarization of (V bl) was by 31±2 mV (n=47).R te fell significantly from 16.4±3.6 to 14.2±3.7 Ω·cm2 (n= 6), andFR blincreased significantly from 0.11±0.02 to 0.51±0.10 (n=6). In the second phase the repolarisation of (V bl) amounted 11±2 mV (n=47) and a steadystate (V bl) of −51±2 mV (n=47) was reached.R te fell further and significantly to a steady-state value of 12.4±3.8 Ω·cm2 (n=6) andFR bl fell significantly to 0.42±0.13 (n=6). In 30% of the experiments, a transient hyperpolarisation of (V bl) by 8±2 mV (n=14) was seen during wash out of adenosine. In the presence of adenosine, but not under control conditions, lowering of luminal Cl− concentration from 120 to 32 mmol/l depolarised (V bl) significantly by 8±1 mV (n=9). Basolateral ATP and ADP (0.1 mmol/l) led to a short initial depolarisation followed by a sustained and significant hyperpolarisation by 6±2 mV (n=27) and 5±4 mV (n=8), respectively. Carbachol (CCH) hyperpolarised (V bl) in a concentration-dependent manner. At 100 μmol/l (bath) the hyperpolarisation was by 14±2 mV (n=11) andFR bl fell slightly. Neurotensin (⩾10 nmol/l), isoproterenol (⩾10 μmol/l) and uridine 5′-triphosphate (UTP, 0.1 mmol/l) had no effect. It is concluded that PGE2, VIP and adenosine upregulate sequentially a luminal Cl− conductance and a basolateral K+ conductance by increasing intracellular cAMP concentration. Ca2+ mobilising hormones such as ATP, ADP, and CCH increase the basolateral K+ conductance, while the effect on luminal Cl− conductance appears to be very limited.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00704154
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  • 15
    Electronic Resource
    Electronic Resource
    Swelling of rat mesangial cells induces a Ca2+-dependent Cl− conductance (1996)
    Springer
    Pflügers Archiv 431 (1996), S. 706-712 
    Details
    ISSN: 1432-2013
    Keywords: Mesangial cell ; Cell swelling ; Ion currents ; Intracellular Ca2+ activity ; Cl− conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Membrane voltage (V m) and ion currents of rat mesangial cells in primary culture were measured with the patch-clamp technique in the fast whole-cell configuration.V m was −44 ± 1 mV (n = 138). A reduction of the osmolality from 290 to 190 mosmol/kg depolarizedV m from −44 ± 1 to −29 ± 1 mV (n = 118) and increased the inward and outward conductances (Gm) from 14±2 to 39 ± 4 nS and 13±2 to 37 ± 4 nS (n = 84), respectively. During the hypotonicity-induced depolarization the cell capacitance increased significantly from 33 ± 3 to 42 ± 4 pF (n = 40). The effect of hypotonic cell swelling onV m was increased in a bath with a reduced extracellular Cl− of 32 mmol/l (by 71 ± 4%,n = 23), indicating that a Cl− conductance was activated. The permselectivity of this conductance was I− ≥ Br− 〉 Cl−. TheV m response was not affected in the presence of a reduced extracellular Na+ of 5 mmol/l (n = 13) and was inhibited in a solution with reduced extracellular Ca2+ concentration (by 63 ± 9%,n = 14). In microfluorescence measurements with the Ca2+-sensitive dye fura-2 hypotonic cell swelling induced a sustained increase of the intracellular Ca2+ activity, [Ca2+]i (n = 19). The increase of [Ca2+]i was completely inhibited when the extracellular solution was free of Ca2+. TheV m response to hypotonic cell swelling was not attenuated in the presence of the L-type Ca2+ channel blockers nicardipine (n = 5), nifedipine (n = 5) and verapamil (n = 5) (all at 1 μmol/l). The data indicate that in rat mesangial cells, osmotic swelling induces a Ca2+ influx from extracellular space. This Ca2+ influx activates a Cl− conductance resulting in a depolarization ofV m. The enhanced Cl− conductance may lead to KCl extrusion and hence regulatory volume decrease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02253833
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  • 16
    Electronic Resource
    Electronic Resource
    Analysing ion channels with hidden Markov models (1994)
    Springer
    Pflügers Archiv 426 (1994), S. 328-332 
    Details
    ISSN: 1432-2013
    Keywords: Cortical collecting duct ; K+ channel ; Rat ; Isolated tubule ; Patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ion channel current amplitudes (μ) and open probabilities (P o) have been analysed so far by defining a 50% threshold to distinguish between open and closed states of the channels. With this standard method (SM) it is very difficult or even impossible to analyse channels of different size in one membrane patch correctly. A stochastical model, named the hidden Markov model (HMM), separates between observation noise and the stochastic process of opening and closing of ion channels. The HMM allows the independent analysis of μ, P o, and mean dwell times (τ) of different channels in one membrane patch, without defining threshold levels. Using this method errors in the analysis are not summarized like in the SM because all different analysing procedures (e. g. filtering, setting of threshold, fitting processes) are done in one step. Two different K+ channels in excised basolateral membranes of the cortical collecting duct of rat (CCD) were analysed by the SM and the HMM. The μ value of the intermediate-conductance K+ channel (i-K+) was 3.9±0.1 pA (SM) and 3.8±0.2 pA (HMM) for 11 observations. The P o value of this channel was 10.2±4.2% (SM) and 10.1±4.0% (HMM). The mean τ values were 5.4±0.6 ms for the open state and 9.6±2.2 ms and 145±21 ms for the closed states (SM) and 7.8±1.1 ms, 7.7±0.9 ms and 148±24 ms (HMM), respectively. For seven small-conductance K+ (s-K+) channels, which were found in the same membrane patches as the i-K+, an accurate analysis of P o and τ was not possible with the SM. The μ value was 1.0±0.1 (SM), 0.9±0.1 (HMM) pA. P o was 16.6±4.6%, the open τ value was 11.1±2.8 ms, and the closed τ value was 34.9±8.5 ms. The HMM allows the analysis of single-channel currents, P o, and mean τ values when different or more than one ion channel(s) are colocalized in one membrane patch. Where analysis with the SM was possible results did not significantly differ from those obtained with the HMM. Thus for this kind of analysis the method of setting a 50% threshold appears justified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374789
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  • 17
    Electronic Resource
    Electronic Resource
    Urate handling by the rat kidney (1974)
    Springer
    Pflügers Archiv 352 (1974), S. 115-120 
    Details
    ISSN: 1432-2013
    Keywords: Urate ; Reabsorption ; Loop of Henle ; Micropuncture ; Microperfusion ; Microinjection ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Reabsorption rates for urate in the loops of Henle were measured in superficial nephrons in the rat 1. under conditions of free flow, 2. using microperfusion and 3. by a microinjection technique. 1. Under conditions of free flow distally measured TF/PUA/TF/PIn-values varied between 0.51 and 0.38 in antidiuretic rats, depending on TF/PIn (UA = both uric acid and urate, In = inulin, TF/P = concentration in tubular fluid to plasma concentration). The corresponding values in samples from end-proximal tubules were 1.06 and in urine 0.19 (U/PUA/U/PIn). 2. In microperfusion experiments of Henle loops early distal recoveries of 2-C14 urate varied between 57 and 86%, depending on the flow rates (10–40 nl/min). 3. In microinjection experiments C14 recovery in urine was about 85% when tracer solution was microinjected into endproximal tubules. From these results we conclude: 1. The main site of urate reabsorption is located in the loops of Henle. 2. This reabsorption is highly dependent on flow rates. Increase of flow rate through Henle's loop decreases urate reabsorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587510
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  • 18
    Electronic Resource
    Electronic Resource
    Urate interaction with plasma proteins and erythrocytes (1974)
    Springer
    Pflügers Archiv 352 (1974), S. 121-133 
    Details
    ISSN: 1432-2013
    Keywords: Urate ; Protein Interaction ; Uptake by Erythrocytes ; Renal Reabsorption ; Man ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Interaction of urate with human and rat plasma was studied by a dialysis technique at different temperatures. At 4° C a certain fraction of urate is bound to proteins. However, this fraction diminishes with increasing temperature and at 37° C only some 7–8% (in man) and 2% (in rat) interact with proteins. The finding that urate is almost completely filtered in the glomerulus is discussed. In body areas exposed to low temperatures protein binding of urate may be of importance. Urate uptake by erythrocytes is characterized by two components: a fast component equilibrating almost immediately at about 7% in man and 17% in rat and a slow component reaching equilibrium after 60 min, at 28% and 36%, respectively. The process is described by a mathematical formula. Lowering of the temperature mainly diminishes uptake by the slow component withQ 10-values ranging between 1.5 and 4.0. In the observed range of concentrations the uptake process does not saturate. The results at lower pH-values suggest that it is unionized uric acid which is transported by the slow component. Application of the data to kidney medulla supports the hypothesis that erythrocytes and, probably, to a lesser extent plasma proteins serve as vehicles for urate reabsorption in the countercurrent system. Such a temporary interaction enables uric acid to escape recirculation and to leave the kidney medulla.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587511
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