Composition of Airway Surface Liquid Determined by X-ray Microanalysis

Abstract

The composition of the airway surface liquid, a thin layer of fluid covering the airway wall, has been debated. Two new techniques to determine the ionic composition of the airway surface liquid are presented. In the first technique, pieces of the airway were shock-frozen and analyzed by X-ray microanalysis in the frozen state in the scanning electron microscope. In the second technique, the airway surface liquid was collected with the help of dextran beads that were allowed to absorb the fluid. The beads were collected in silicon oil, cleaned, dried, and analyzed. Airway surface liquid from pig airways was isotonic to lightly hypertonic, whereas airway surface liquid from mouse and rat airways was hypotonic. The ionic composition of airway surface liquid from rodent airways could be changed by pharmacological stimulation of fluid transport. Transgenic mice with cystic fibrosis (CF) had significantly higher Na and Cl concentrations in the airway surface liquid than normal mice. Nasal fluid was also collected from humans. In CF patients, CF heterozygotes, and rhinitis patients, the levels of Na and Cl in the nasal fluid were signifi- cantly higher than in healthy controls. In CF patients K levels were also significantly higher than in healthy controls. The ionic concentrations in fluid collected from patients with primary ciliary dyskinesia (PCD) were not different from normal. Females with CF had significantly higher concentrations of Na, Cl and K in their nasal fluid compared to male patients. The dextran bead technique was also used to determine the ionic composition of the apical fluid in cultures of respiratory epithelial cells from healthy controls and CF patients. In the healthy controls, the fluid was hypotonic. In the CF cell cultures, the apical fluid had a higher Na and Cl concentration than in the controls.

Capillary electrophoresis analysis of biofluids with a focus on less commonly analyzed matrices

“…Initially it appeared that there may be some systematic bias between the filter-paper and capillary sampling techniques [43], since generally isotonic levels of inorganic ions were determined using filter paper sampling in dogs, while those determined in rats by capillary sampling were hypotonic. Recent results using ion exchange beads to harvest ASF and X-ray microanalysis to determine inorganic ions in the collected sample [47,48] are generally in agreement with data collected in large animals by the filter paper technique and in rodents using capillary sampling and CE, leading to the conclusion that both approaches are producing essentially reliable results and that the differences observed truly reflect inter-species differences.…”

In Situ Measurement of Airway Surface Liquid [K+] Using a Ratioable K+-sensitive Fluorescent Dye

“…measured in the ASL of intact pig and mouse trachea confirmed the major conclusion from measurements on airway epithelial cell cultures. Previous estimates of ASL [K ϩ ] in tracheas of pig, rat, and mouse by x-ray microanalysis were ϳ20, 13, and 28 mM, respectively (32). ASL [K ϩ ] measurement by flame photometry following ASL sampling of human trachea and bronchi by filter paper gave ASL [K ϩ ] of ϳ22 mM (5).…”

Effect of ionic compositions in nasal irrigations on human olfactory thresholds

“…Cystic fibrosis (CF) provides another prominent example of a genetic mutation involving a specific TCNIC that classically results in CRS through abnormal mucociliary clearance. Although CF pathophysiology involves mutations of a transmembrane chloride ion transporter, CF patients, whose nasal liquid also consists of increased potassium concentrations, often report olfactory loss . In patients with these single‐gene defects, the dysfunctional ionic regulation within the upper and lower airways certainly extends to the olfactory cleft and increases the likelihood of olfactory impairment as a part of CRS symptomatology.…”