Fachbereich Veterinärmedizin



    Regulation of a non-selective cation channel in cells of the ovine rumen epithelium by PGE2 and Forskolin (2005)

    Stumpff, F
    Brinkmann, I
    Martens, H
    Jahrestagung der Deutschen Physiologischen Gesellschaft
    Göttingen, 06. – 09.03.2005
    Pflügers Archiv : European journal of physiology — S. S116
    ISSN: 1432-2013
    URL (Volltext): http://www.physiologische-gesellschaft.de/
    Institut für Veterinär-Physiologie

    Oertzenweg 19 b
    14163 Berlin
    Tel.+49 30 838 62600 Fax.+49 30 838-62610

    Abstract / Zusammenfassung

    We have recently shown that reduction of cytosolic magnesium
    enhances current through an apical non-selective cation channel
    in ruminal epithelium. To investigate effects of cAMP, cultured
    cells were studied using the whole cell configuration of the patchclamp
    technique. Cells filled with choline chloride solution
    (ChCl) that contained both Mg (0.9 mM) and Na-cAMP (1 mM)
    had significantly higher reversal potentials (27±3 mV) than
    controls filled with Mg-free solution, with or without cAMP
    (p<<0.01). Unlike in cAMP-free controls, both current at -47 mV
    and reversal potential were reduced by replacing Na with Ch in
    the external solution (p(Na)/p(Ch)=1.09±0.08 (cAMP-free, n=9);
    p(Na)/p(Ch)=1.7±0.2 (cAMP, n=11); p=0.01). Internal
    application of cAMP doubled permeability of Na versus K from
    0.34±0.02 to 0.76±0.04 (p=0.0001, n=4), with corresponding
    effects on p(K)/p(Ch). Application of PGE2 (4mM) increased
    inward current at -47 mV by -6±1 pA/pF and reversal potential
    by 17±1 mV(0.00006, n=7, pipette: Kglu); -15±5 pA/pF and 33±4
    mV(p=0.002, n=8, CsCl) and -23±8 pA/pF and 20±1
    mV(p=0.0002, n=5, ChCl). Forskolin (10 mM) had similar
    effects. We conclude that PGE2, forskolin and elevation of cAMP
    increase the selectivity of the non-selective cation channel in
    rumen epithelium for sodium. Endogenous cAMP may be
    essential for the physiological function of these channels,
    allowing uptake of sodium while minimizing efflux of potassium.