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Ruminal epithelial cells express high conductance chloride channel
Author(s) -
Stumpff Friederike,
Martens Holger,
Gaebel Gotthold
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.2_supplement.136
Subject(s) - dids , chloride , chloride channel , chemistry , patch clamp , conductance , transepithelial potential difference , reversal potential , biophysics , rumen , membrane potential , tetraethylammonium chloride , medicine , fermentation , ion transporter , biochemistry , biology , potassium , membrane , receptor , mathematics , organic chemistry , combinatorics
Uptake of anions across the wall of the rumen of sheep and cows is essential for the maintenance of ruminal fermentation. In order to characterise a previously identified anion channel in more detail (Am J Physiol 289: 3, G508‐20, 2005), isolated cells of the ruminal epithelium were studied using the patch clamp technique. Cells were filled with Nagluconate solution and superfused with NaCl Ringer. Removal of external chloride reversibly depolarised the cells from −32 ± 1 mV to 2.9 ± 1 mV (n = 40, p<0.001), while outward current at 100 mV dropped from 2.1 ± 0.2 pA/pF to 0.7 ± 0.1 pA/pF (p < 0.001). Application of DIDS (1 mM) reduced current at 100 mV by 1.3 ± 0.3 pA/pF (p<0.001, n=20) with a smaller reduction at 100 μM (0.8 ± 0.3 pA/pF, n=5). Replacement of either 10 mM or 130 mM chloride with NO 3 − had no impact on reversal potential or outward current. Replacement of chloride by HCO 3 − reduced outward current by 1.1 ± 0.3 pA/pF with reversal potential at −21 ± 2 mV (n=7; p=0.01 versus NaCl and p=0.001 versus Nagluconate). Excised inside out patch‐clamp experiments in symmetrical and assymetrical NMDG‐anion solutions showed channels with a conductance of 350 ± 7 pS for chloride. We conclude that isolated cells of the ruminal epithelium express an anion channel with p(Cl − ) ≈ p(NO 3 − ) > p(HCO 3 − ) > p(gluconate − ). This channel may play a role in the basolateral efflux of anions from the rumen.