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  • 1
    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: Key words 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 depolarized V m from −44 ± 1 to −29 ± 1 mV (n = 118) and increased the inward and outward conductances (G m) 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 on V 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−. The V 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+. The V 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 of V 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/s004240050055
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  • 2
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of depolarizing and hyperpolarizing agents on the membrane potential difference of primary cultures of rabbit aorta vascular smooth muscle cells (1991)
    Springer
    Pflügers Archiv 419 (1991), S. 69-75 
    Details
    ISSN: 1432-2013
    Keywords: Vascular smooth muscle cells ; Membrane potential ; Cromakalim ; Glibenclamide ; K+ channels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Vascular smooth muscle cells of rabbit aorta were enzymatically dispersed, kept in primary culture, and studied between days 1 and 7 in a bath rinsed with Ringer-like solution at 37°C. The electrical membrane potential difference (PD) was measured with microelectrodes. The mean value of PD was −50±0.4 mV (n=53). Cromakalim (BRL 34915), 1 μmol/l and 10 μmol/l, hyperpolarized the membrane potential by 9±1 mV (n=11) and 15±1 mV (n=53) respectively. Glibenclamide (10 μmol/l) abolished the hyperpolarizing effect of cromakalim (n=6). Simultaneous addition of cromakalim and glibenclamide (both 10 μmol/l, n=11) and glibenclamide itself (10 μmol/l, n=7) had no effect on PD. In patch-clamp experiments in outside-out-oriented Ca2+-sensitive K+ channels, cromakalim increased the open probability (P o) only slightly and only with a cytosolic Ca2+ activity of 1 μmol/l. In all other series cromakalim had no effect on the P o of these channels. Forskolin (10 μmol/l) hyperpolarized PD by 6±1 mV (n=13). The nucleotides UTP, ATP and ITP (10 μmol/l) depolarized PD by 12±1 mV (n=7), 8±1 mV (n=65) and 5±1 mV (n=6) respectively. GTP, [α,β-methylene]ATP and adenosine had no significant effect. Mn2+ (1 mmol/l, n=18), Ni2+ (1 mmol/l, n=13), Co2+ (1 mmol/l, n=11), Zn2+ (1 mmol/l, n=6) and the Ca2+-channel blockers verapamil and nifedipine (both 0.1 mmol/l, n=6) did not attenuate the depolarization induced by 10 μmol/l ATP. Fetal calf serum (100 ml/l, n=7) depolarized PD by 11±2 mV. This effect was not abolished by nifedipine or by replacing NaCl by choline chloride. The data indicate that PD of vascular smooth muscle cells is depolarized by P2 agonists and hyperpolarized by the K+-channel opener cromakalim. The effect of cromakalim is antagonized by glibenclamide. The effect of cromakalim is probably not mediated by the K+ channel identified in excised patches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373749
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  • 4
    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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  • 5
    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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    Paper (German National Licenses)
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