MUCOCILIARY INTERACTION INVITRO - EFFECTS OF PHYSIOLOGICAL AND INFLAMMATORY STIMULI

Mucociliary transport in the airways is governed by the interaction between ciliary activity and the depth and rheological properties of the liquids (mucus) covering the epithelial surface. A change in one of these parameters may not predict the direction and magnitude of a concomitant change in mucociliary transport. We therefore determined the effects of physiological (neurotransmitters) and pathological (inflammatory mediators) stimuli on ciliary beat frequency (CBF), surface liquid velocity (SLV), surface liquid depth (SLD), and viscoelasticity of mucus in pieces of sheep trachea (n = 5 for each treatment) mounted in a chamber such that the submucosal side was bathed with Krebs-Henseleit perfusate (KH) and the luminal side was exposed to conditioned air. SLV, SLD, and CBF were measured with a microscope provided with an electronic micrometer and strobe light. Apparent viscosity and shear elastic modulus were measured with a microcapillary method using mucus collected at the downstream end of the preparation. Control CBF, SLV, and SLD were 11.6 ± 0.4 (SE) Hz, 91 ± 8 μm/s, and 33 ± 5 μm, respectively, at base line and did not change during KH perfusion for 100 min. Perfusion with both acetylcholine and epinephrine (10-5 to 10-3 M) produced concentration-dependent increases in mean CBF (maximum increases at 10-3 M of 16 and 9%, P < 0.05), whereas only acetylcholine increased mean SLV (+56% at 10-3 M, P < 0.05). Perfusion with platelet-activating factor (10-7 to 10-5 M) decreased both CBF and SLV in a dose-dependent fashion (-6 and -63% at 10-5 M, P < 0.05), whereas antigen perfusion (1:60 dilution) increased mean CBF (+10%, P < 0.05) but decreased SLV (-47%, P < 0.05). Mean SLD was not altered during, and significant changes in viscoelastic values were not detected after, any of the challenges. These results suggest that physiological and inflammatory stimuli have different short-term effects on the various components of mucociliary interaction. Therefore, an alteration of one parameter of mucociliary transport cannot always be translated into a complementary change of another parameter.