Tracheal mucus rheology and epithelial potential difference in two day old puppies1
Issue title: Proceedings of the Seventh International Congress of Biorheology. Part I. Palais des Congrès, Nancy, France, 18–23 June 1989. Dedicated to Richard Skalak
Guest editors: Alfred L. Copley and Jean-François Stoltz
Affiliations: Pulmonary Defense Group, 519 Newton Research Bldg., University of Alberta, Edmonton, Canada T6G 2C2
Note: [1] Supported by Canadian Cystic Fibrosis Foundation.
Note: [*] With the technical assistance of Oscar Ramirez.
Note: [] Accepted by: Editor E. Puchelle
Abstract: The transepithelial potential difference (PD) value represents an integral of ion fluxes across the epithelium, and relates to the regulation of airway fluid. We studied six healthy two day old husky puppies for their tracheal mucus rheology and bioelectric properties, since this data in newborns are still unknown. PD (-mV, epithelium vs. subcutaneous space) was measured using the agar bridge technique in two locations - lower trachea and subglottic region. For the rheological analysis, the magnetic microrheometer was employed; data are presented as mechanical impedance log G* and loss tangent tan δ (1 rad/s). The mucus collection rate (mg/min) and the solid content (%) were determined by gravimetry. Mucociliary clearability, normalized to frog mucus, (MCFP) was determined directly by the frog palate method; a cough clearability index (CCI) was computed from simulated cough machine data obtained with mucus-like gels. The mucus collection rates and PD values were considerably lower than those observed in adult dogs; the mechanical impedance values were also reduced in comparison with adult data. The PD profile (-13.9 ± 1.2 mV lower trachea vs. -18.4 ± 1.4 mV subglottical, i.e. more negative subglottically), however, is similar to that observed in adult dogs. Intratracheal profiles in mucus collection rate and mucus rheology were also comparable between puppies and adult dogs. The low collection rates in puppies, particularly in lower trachea, could indicate either reduced mucus volume or slower clearance. PD and collection rate correlated very strongly (r = 0.82, p = 0.0003). PD also correlated negatively with log G* (r = 0.73, p = 0.003) and positively with tan δ (r = 0.58, p = 0.03). MCFP and % solids correlated positively (r = 0.84, p = 0.0012), in contradistinction to the usual relationship, perhaps due to the presence of non-glycoprotein components that do not contribute to crosslink formation. The apparent maturation of airway bioelectric properties, mucus collection rate and mucus viscoelasticity are all consistent with the maturation of mucociliary clearance, which has previously been reported.
