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Related Concept Videos

Bicarbonate-Carbonic Acid Buffer01:22

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Respiratory compensation is a vital physiological process that stabilizes blood plasma pH by regulating the partial pressure of carbon dioxide (PCO2), a key determinant of pH levels. Most carbon dioxide in the blood dissolves and converts into carbonic acid (H2CO3). It dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3⁻). There is also an inverse relationship between PCO2​​ and pH.
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Chloride ions contribute to the osmotic pressure gradient distinguishing the intracellular fluid (ICF) from the extracellular fluid (ECF). They counterbalance positively charged ions in the ECF and ensure its electrochemical stability. The renal system's process of chloride absorption and release generally mirrors that of sodium ions.
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Breathing01:05

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The process of breathing, inhaling and exhaling, involves the coordinated movement of the chest wall, the lungs, and the muscles that move them. Two muscle groups with important roles in breathing are the diaphragm, located directly below the lungs, and the intercostal muscles, which lie between the ribs. When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity and creating more room for the lungs to expand. When the intercostal muscles contract, the ribs...
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Renal Regulation of Acid-Base Balance01:29

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Real-Time, Semi-Automated Fluorescent Measurement of the Airway Surface Liquid pH of Primary Human Airway Epithelial Cells
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Real-Time, Semi-Automated Fluorescent Measurement of the Airway Surface Liquid pH of Primary Human Airway Epithelial Cells

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Native small airways secrete bicarbonate.

A K M Shamsuddin1, Paul M Quinton

  • 11 Department of Pediatrics, University of California San Diego, La Jolla, California; and.

American Journal of Respiratory Cell and Molecular Biology
|November 15, 2013
PubMed
Summary
This summary is machine-generated.

Bicarbonate (HCO3(-)) secretion in small airways is constitutively active and can be stimulated by cAMP and Ca(2+) agonists. This suggests dual mechanisms for airway surface liquid regulation in cystic fibrosis (CF).

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Area of Science:

  • Pulmonary Physiology
  • Epithelial Transport
  • Cystic Fibrosis Research

Background:

  • Cystic Fibrosis (CF) pathology is primarily linked to epithelial chloride (Cl(-)) transport defects.
  • Bicarbonate (HCO3(-)) transport dysfunction also significantly contributes to CF pathogenesis, particularly in exocrine organs.
  • Little is known about HCO3(-) secretion in small airways, a key site of CF morbidity.

Purpose of the Study:

  • To investigate the properties and regulation of HCO3(-) transport in native porcine small airways.
  • To determine if HCO3(-) secretion occurs constitutively and can be modulated by physiological agonists.

Main Methods:

  • Utilized a novel mini-Ussing chamber system to measure HCO3(-) transport in small airway segments (∼1 mm diameter).
  • Assayed HCO3(-) secretion via transepithelial voltage, conductance, and equivalent short-circuit current under specific ionic conditions.
  • Employed selective agonists and inhibitors to identify regulatory pathways (cAMP and Ca(2+)).

Main Results:

  • Demonstrated constitutive HCO3(-) secretion in small airway epithelia.
  • Showed significant stimulation of HCO3(-) secretion by both β-adrenergic (cAMP-mediated) and purinergic (Ca(2+)-mediated) agonists, acting independently.
  • Identified two distinct components of HCO3(-) secretion.

Conclusions:

  • Small airways possess physiologically regulated mechanisms for HCO3(-) secretion.
  • These mechanisms likely involve CFTR- and calcium-activated pathways, crucial for maintaining airway surface liquid homeostasis.
  • HCO3(-) secretion plays a vital role in mucus clearance and innate antimicrobial defense in small airways.