Mechanisms of sodium and chloride transport across equine tracheal epithelium.
Abstract: Equine tracheal epithelium, stripped of serosal muscle, mounted in Ussing chambers, and bathed in plasmalike Ringer solution generates a serosa-positive transepithelial potential of 10-22 mV and a short-circuit current (Isc) of 70-200 microA/cm2. Mucosal amiloride (10 microM) causes a 40-60% decrease in Isc and inhibits the net transepithelial Na flux by 95%. Substitution of Cl with gluconate resulted in a 30% decrease in basal Isc. Bicarbonate substitution with 20 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid decreased the Isc by 21%. The Cl-dependent Isc was inhibited by serosal addition of 1 mM amiloride. Bicarbonate replacement or serosal amiloride (1 mM) inhibits the net Cl flux by 72 and 69%, respectively. Bicarbonate replacement significantly reduces the effects of serosal amiloride (1 mM) on Isc, indicating its effect is HCO3 dependent. Addition of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP; 100 microM) causes a 40% increase in Isc. This effect is inhibited by subsequent addition of 10 microM serosal bumetanide. Bumetanide (10 microM) reduces net Cl secretion following stimulation with 8-BrcAMP (100 microM). Serosal addition of BaCl2 (1 mM) causes a reduction in Isc equal to that following Cl replacement in the presence or absence of 100 microM cAMP. These results suggest that 1) Na absorption depends on amiloride-inhibitable Na channels in the apical membrane, 2) Cl influx across the basolateral membrane occurs by both a Na-H/Cl-HCO3 parallel exchange mechanism under basal conditions and by a bumetanide-sensitive Na-(K?)-Cl cotransport system under cAMP-stimulated conditions, and 3) basal and cAMP-stimulated Cl secretion depends on Ba-sensitive K channels in the basolateral membrane.
Publication Date: 1990-12-01 PubMed ID: 2260677DOI: 10.1152/ajplung.1990.259.6.L459Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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The study investigates how sodium and chloride are transported across the equine tracheal epithelium, using different biochemical tests to ascertain how these two elements move across the epithelium under various conditions.
Methods
- The researchers used stripped equine tracheal epithelium mounted in Ussing chambers, and bathed in plasmalike Ringer solution.
- They varied the external environment of the tissue, manipulating the concentration of ions and using compounds such as amiloride, bicarbonate, and 8-bromoadenosine cyclic monophosphate (BrcAMP) to perturb the system and observe their effects on sodium and chloride transport.
Findings
- Equine tracheal epithelium generates a serosa-positive transepithelial potential and a quantifiable current under normal conditions.
- The addition of amiloride to the mucosal side caused a significant decrease in the net charge transport and inhibited the transport of sodium by 95%, suggesting that sodium absorption depends on amiloride-inhibitable sodium channels in the epithelial layer.
- Switching chloride ions with gluconate resulted in a reduction of the baseline charge, implying that chloride ions contribute substantially to the baseline charge transport.
- When bicarbonate was replaced, there was a reduction in the current, which suggests that bicarbonate also plays a role in charge transport. The resulting current was found to be dependent on the presence of bicarbonate, as shown by reduced effects of amiloride on the current in the absence of bicarbonate.
- Moreover, when 8-BrcAMP was added, it led to an increase in the current, indicating that it plays a role in ion transport across the epithelium.
Conclusions
- Under normal conditions, chloride influx across the basolateral membrane occurs due to a parallel exchange mechanism between sodium-hydrogen and chloride-bicarbonate.
- Under conditions stimulated by cAMP, chloride influx occurs due to a bumetanide-sensitive sodium-potassium-chloride cotransport system.
- The data suggests both basal and cAMP-stimulated chloride secretion depends on barium-sensitive potassium channels in the basolateral membrane. This is indicated by the reduction in the current when barium chloride was added to the serosal side.
Cite This Article
APA
Tessier GJ, Traynor TR, Kannan MS, O'Grady SM.
(1990).
Mechanisms of sodium and chloride transport across equine tracheal epithelium.
Am J Physiol, 259(6 Pt 1), L459-L467.
https://doi.org/10.1152/ajplung.1990.259.6.L459 Publication
Researcher Affiliations
- Department of Veterinary Biology, University of Minnesota, St Paul 55108.
MeSH Terms
- 8-Bromo Cyclic Adenosine Monophosphate / pharmacology
- Amiloride / pharmacology
- Animals
- Biological Transport / drug effects
- Bumetanide / pharmacology
- Chlorides / metabolism
- Dogs
- Epithelial Cells
- Epithelium / drug effects
- Epithelium / physiology
- Epithelium / ultrastructure
- Horses / physiology
- In Vitro Techniques
- Kinetics
- Microscopy, Electron
- Models, Biological
- Muscle, Smooth / cytology
- Muscle, Smooth / physiology
- Sodium / metabolism
- Trachea / cytology
- Trachea / physiology
Grant Funding
- AM-38197 / NIADDK NIH HHS
Citations
This article has been cited 8 times.- Bartoszewski R, Matalon S, Collawn JF. Ion channels of the lung and their role in disease pathogenesis.. Am J Physiol Lung Cell Mol Physiol 2017 Nov 1;313(5):L859-L872.
- Brune K, Frank J, Schwingshackl A, Finigan J, Sidhaye VK. Pulmonary epithelial barrier function: some new players and mechanisms.. Am J Physiol Lung Cell Mol Physiol 2015 Apr 15;308(8):L731-45.
- Åstrand AB, Hemmerling M, Root J, Wingren C, Pesic J, Johansson E, Garland AL, Ghosh A, Tarran R. Linking increased airway hydration, ciliary beating, and mucociliary clearance through ENaC inhibition.. Am J Physiol Lung Cell Mol Physiol 2015 Jan 1;308(1):L22-32.
- Huang J, Shan J, Kim D, Liao J, Evagelidis A, Alper SL, Hanrahan JW. Basolateral chloride loading by the anion exchanger type 2: role in fluid secretion by the human airway epithelial cell line Calu-3.. J Physiol 2012 Nov 1;590(21):5299-316.
- Shan J, Liao J, Huang J, Robert R, Palmer ML, Fahrenkrug SC, O'Grady SM, Hanrahan JW. Bicarbonate-dependent chloride transport drives fluid secretion by the human airway epithelial cell line Calu-3.. J Physiol 2012 Nov 1;590(21):5273-97.
- Frizzell RA, Hanrahan JW. Physiology of epithelial chloride and fluid secretion.. Cold Spring Harb Perspect Med 2012 Jun;2(6):a009563.
- Hollenhorst MI, Richter K, Fronius M. Ion transport by pulmonary epithelia.. J Biomed Biotechnol 2011;2011:174306.
- Cuthbert AW, Supuran CT, MacVinish LJ. Bicarbonate-dependent chloride secretion in Calu-3 epithelia in response to 7,8-benzoquinoline.. J Physiol 2003 Aug 15;551(Pt 1):79-92.
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