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    Luminal hyperosmolarity decreases Na transport and impairs barrier function of sheep rumen epithelium (2005)

    Art
    Zeitschriftenartikel / wissenschaftlicher Beitrag
    Autoren
    Schweigel, Monika
    Freyer, Markus
    Leclercq, Sabine
    Etschmann, Benjamin
    Lodemann, Ulrike
    Böttcher, Almut
    Martens, Holger
    Quelle
    Journal of Comparative Physiology B, Biochemical, Systemic, and Environmental Physiology; 175(8) — S. 575–591
    ISSN: 0174-1578
    Sprache
    Englisch
    Verweise
    Pubmed: 16177895
    Kontakt
    Institut für Veterinär-Physiologie

    Oertzenweg 19 b
    14163 Berlin
    Tel.+49 30 838 62600 Fax.+49 30 838-62610
    email:physiologie@vetmed.fu-berlin.de

    Abstract / Zusammenfassung

    The effects of luminal hyperosmolarity on Na and Cl transport were studied in rumen epithelium of sheep. An increase of luminal osmotic pressure with mannitol (350 and 450 mosm/l) caused a significant increase of tissue conductance, G (T), which is linearly correlated with flux rates of (51)Cr-EDTA and indicates an increase of passive permeability. Studies with microelectrodes revealed, that an increase of the osmotic pressure caused a significant increase of the conductance of the shunt pathway from 1.23 +/- 0.10 (control) to 1.92 +/- 0.14 mS cm(-2) (450 mosm/l) without a change of fractional resistance. Hyperosmolarity significantly increased J (sm) and reduced J (net) Na. The effect of hyperosmolarity on J (ms) Na is explained by two independent and opposed effects: increase of passive permeability and inhibition of the Na(+)/H(+) exchanger. Hypertonic buffer solution induced a decrease of the intracellular pH (pH(i)) of isolated ruminal cells, which is consistent with an inhibition of Na(+)/H(+) exchange, probably isoform NHE-3, because NHE-3-mRNA was detectable in rumen epithelium. These data are in contrast to previous reports and reveal a disturbed Na transport and an impaired barrier function of the rumen epithelium, which predisposes translocation of rumen endotoxins and penetration of bacteria.