Effect of increased pressure on tracheal ciliary beat frequency.

Effects of increased ambient pressure on mucociliary clearance have been poorly investigated. The effects of increasing pressures on ciliary beat frequency (CBF) of guinea-pig tracheal rings were studied in vitro. Increased pressures of 25 and 100 kPa induced a significant and equivalent enhancement of CBF from 30 min after the pressure increase. The increase in CBF observed after a pressure increase of 50 kPa (inspiratory oxygen fraction = 21%), was significantly greater than that observed with an equivalent oxygen tension at atmospheric pressure, i.e. with a gas mixture containing 30% oxygen. Addition of N(G)-nitro-L-arginine methylester (L-NAME) inhibited the enhancement in CBF observed after the 25 kPa pressure increase. Addition of L-arginine reversed the effect of L-NAME. These results demonstrate that a pressure increase applied to tracheal rings, in vitro, induces an enhancement of ciliary beat frequency and that generation of nitric oxide may be involved in this ciliary stimulation.