ISSN:
1432-2013
Keywords:
Tracheal epithelium
;
Na+ and Cl− transport
;
Furosemide
;
Amiloride
;
Histamine
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The active transport of Na+ and Cl− across the tracheal epithelium of the cow was investigated in vitro, using the short-circuit technique, by means of ion substitutions, transport inhibitors and by measuring22Na and36Cl fluxes. Under short-circuit conditions, short-circuit current (i o) was 168±5μA cm−2 (mean±SEM,n=30), i.e. 6.2±0.2 μEq h−1cm−2 and resistance (R) was 248±10Ωcm2. Net Na+ flux toward the submucosa (J Na net L-S ) and net Cl− flux toward the lumen (J Cl net S-L ) were of the same magnitude, i.e. 2.7±0.2 and 2.9±0.2 μEq h−1 cm−2, respectively. The permeability coefficients were 3.6·10−6 forP Na and 7.8·10−6 cm s−1 forP Cl. Under open-circuit conditions, the transepithelial electrical potential difference (ΔΨ) was 43±2 mV (lumen negative,n=20).J Na net L-S andJ Cl net S-L were close to zero. Bilateral substitution of Cl− with SO 4 2− or isethionate, or administration of furosemide 5·10−3M or bumetanide 10−4M in the submucosal bathing medium produced a 40 to 50% decrease ini 0; furosemide abolishedJ Cl net S-L . Bilateral substitution of Na+ with choline or Mg2+, or addition of ouabain 10−4M to the submucosal bath abolishedi 0;J Na net L-S andJ Cl net S-L were suppressed by ouabain. Amiloride 10−4M in the luminal bath reducedi 0 by 23% and diminishedJ Na net L-S by 80%. Histamine 10−4M, added to the submucosal bathing medium, reducedJ Na net L-S and increasedJ Cl net S-L , under short-circuit conditions. In open-circuit conditions, histamine had little effect on ion fluxes. This substance had no effect on the electrical properties, as shown previously. These results are consistent with the model proposed by Silva et al. [20] for a Cl−-secreting, Na+-reabsorbing epithelium.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00584698
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