Ionic composition of rat airway surface liquid determined by X-ray microanalysis

Abstract

The thin layer of liquid that lines the conducting airway epithelium, the airway surface liquid (ASL), is important for mucociliary clearance. Altered ionic composition and/ or volume of the ASL play a major role in the pathology of airway diseases such as cystic fibrosis. Since the ASL is a thin layer, it has been difficult to exactly determine its composition. The present paper describes two techniques that have been developed and used to study ASL composition: X-ray microanalysis of frozen hydrated rat trachea, and an ion-exchange (dextran) bead method, where dextran beads were placed on the airway epithelium to equilibrate with the ASL; the beads were then collected under silicone oil, dried and analyzed by X-ray microanalysis. The results from both frozen-hydrated specimens and from the dextran beads showed that ASL from rat trachea is hypotonic. Concentrations of Na, P, S, and K were higher in the frozen-hydrated ASL, in which mainly the mucus layer is analyzed, compared with the dextran bead method, in which mainly the periciliary liquid is sampled. Also the composition of rat nasal fluid was investigated by the dextran bead method. This fluid was somewhat hypertonic because of a high K concentration. The ionic composition of the nasal and tracheal fluid can be manipulated by cholinergic or alpha- or beta-adrenergic stimulation. Collecting ASL with dextran beads did not disturb the integrity of the airway epithelium. The ionic composition of the collected beads remained stable for several days during storage in silicone oil. It is concluded that X-ray microanalysis is a suitable method to determine the ionic composition of ASL.

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.…”

Transient receptor potential vanilloid 4 regulates aquaporin-5 abundance under hypotonic conditions

“…The absolute osmolality of the airway surface liquid (ASL) has proven difficult to determine. Recent reports in mouse (42,43) and rat (44) airways indicate that ASL osmolality is hypotonic in basal conditions, whereas others suggest it is isotonic (32,45). More certainly, when ventilation is increased, for example with exercise, the ASL osmolality increases (31,32,46), with return to basal levels with cessation.…”

Composition of Airway Surface Liquid Determined by X-ray Microanalysis

“…In the rat experiments, adult Sprague-Dawley rats (male and female, 7-8 weeks old, 250-300 g), were used [24].…”

“…Nasal fluid of mouse and rat was collected in Sephadex beads in the following way [22,24]: The Sephadex G-25 beads were applied to double-sided tape attached to a filter paper (width 1-2 mm, length 5 mm). The filter paper with the Sephadex beads was inserted into either one or both nostrils of the mouse, beads facing the nasal septum, and kept there for 10 min.…”