Physiological role of NO in the airway epithelia

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The upper airway epithelium largely consist of ciliated columnar cells. These cells are famous for the clearance function in the airway. The beating of cilia conveys and clears foreign bodies up to the pharynx. Inside the ciliated columnar cell, there are densely populated mitochondria which keep providing ATP to support the strenuous movement of the cilia. In order to investigate the function of the epithelium of the upper airway, we attempted to measure the 02 consumption and C02 production of epithelia with using a ventilatory gas sampling technique of nasal cavity. The nostrils were ventilated from one side to the other by an air-pump while the soft palate was voiuntarily closed by the subject. The sample gases were continuously monitored with a mass spectormeter and a NO analyzer for a real-time analysis of VO2, VCO2 and VNO on the MacLab system. VO2 was 1.2() SY. +-. []0.15 and VCO2 was 1.65 () SY. +-. [] 0.10 ml/min (mean () SY. +-. [] SD). R was 1.38 () SY. +-. [] 0.12. VNO was 537 () SY. +-. [] 1 13 (ml/min/nose). Anoxia evoked simultaneous reduction of VO2, VCO2 and VNO. This suggests that the partial pressure of oxygen in the airway is the major deteminant for the metabolism of the lining epithelium. The physiological significance of lower airway NO was aiso investigated in the isolated rabbit lung and the effect of anoxia (hypoxia) was found to be similar. VNO of exhaled NO varies with the level of airway O2 in the manner of Michaelis-Menten kinetics. We also found the linearity between PO2 and changes of pumonary artery pressure. These findings strongly suggest that epithelial NO is sensing the oxygen level in the airway and play a pivotal role in matching ventilation and perfusion.