Ambient oxygen regulates epithelial metabolism and nitric oxide production in the human nose

Abstract

The effects of ambient O2tension on epithelial metabolism and nitric oxide (NO) production (V˙no) in the nasal airway were examined in nine healthy volunteers. Nasal V˙no, O2consumption (V˙o2), and CO2production (V˙co2) were measured during normoxia followed by gradual hypoxia from 21 to 0% O2concentration. Nasal V˙o2,V˙co2, and respiratory quotient during normoxia were determined to be 1.19 ± 0.04 ml/min, 1.60 ± 0.04 ml/min, and 1.35 ± 0.04, respectively. Hypoxia exposure to the nasal cavity significantly decreased bothV˙co2and V˙no[V˙co2: 1.60 ± 0.04 to 0.96 ± 0.03 ml/min ( P < 0.01), V˙no: 530 ± 15 to 336 ± 9 nl/min ( P < 0.01)].V˙no was reduced commensurately with gradual decline in O2tension, and the apparent Kmvalue for O2was determined to be 23.0 μM. These results indicate that the nasal epithelial cells exchange O2and CO2with ambient air in the course of their metabolism and that nasal epithelial cells can synthesize NO by using ambient O2as a substrate. We conclude that air-borne O2diffuses into the epithelium where it may be utilized for either cell metabolism or NO synthesis.