Rheological determinants of mucociliary transport in the nose of the rat.

The present work was designed to investigate whether the rheological determinants for nasal mucociliary transport are the same in the intact preparation (in situ), as they are when the mucus is added exogenously to the isolated, mucus-depleted frog palate (in vitro). We evaluated the association between estimators of mucociliary transport in both conditions and rheological parameters using multiple regression techniques. Two kinds of rats were used: (a) specific pathogen free (SPF) rats, representing the normal condition of respiratory epithelium; (b) non-SPF rats (NSPF), which have a chronic inflammatory process in the airways. In situ mucociliary clearance (MCC) was determined by measuring the displacement of charcoal particles placed in the nasal septum. In vitro mucociliary transport (MCT) of rat nasal mucus was measured using the isolated frog palate preparation. Mucus rheologic properties were determined by magnetic microrheometry, in oscillatory deformations performed at 1, 10 and 100 radians/sec. No differences were detected between SPF and NSPF rats in terms of rheological parameters. A decreased MCC was found in NSPF in comparison with the SPF group, but no differences were observed between groups in terms of MCT, as could be predicted by rheological data. When all animals were pooled, in situ transport was significantly associated with the viscosity/elasticity ratio, whereas in vitro transport was dependent on the total mechanical impedance of the mucus sample. In conclusion, in situ mucus transport is influenced by other rheological parameters than those associated with in vitro transportability.