| The main goal of this dissertation was to understand the relationship between nasal mucus composition and fraction of O3 absorbed in the nose (Λnose). We believe that Λnose is controlled by the composition of the fluid lining the nasal cavity. Urate has been identified as the major low molecular weight antioxidant in nasal mucus and, therefore, we hypothesize that Λnose is heavily influenced by the concentration of urate and possibly by other antioxidants such as ascorbate and protein thiols present in this fluid. To test this hypothesis a nasal exposure system was developed to measure Λnose during unidirectional flow from the right to the left nostril, while the subject maintained the velopharyngeal aperture closed, and a nasal washing method was employed to sample the nasal mucus.; The initial experiments were carried out on 10 healthy non-smokers to characterize the effect of flowrate on Λnose. These experiments showed a decrease in the mean ± SE of Λnose for the pooled subject data from 0.80 ± 0.02 to 0.33 ± 0.02 with an increase in flowrate from 3 to 15 LPM. A one-dimensional steady state model applied to the flowrate data showed that the gas phase diffusion resistance in this unidirectional gas flow was less than 24% of the overall diffusion resistance, indicating that simultaneous diffusion and chemical reaction of O3 in the mucous layer was the limiting factor in the uptake process.; Natural variations in Λnose on different days among a group of 15 healthy non-smokers amounted to a mean ± SE of 0.634 ± 0.002 at 5 LPM and 0.444 ± 0.001 at 10 μM. For all the subjects in the study, the fluid collected from the nasal washings contained a mean ± SE of urate, ascorbate, and total protein levels of 15.03 ± 1.40μM, 1.88 ± 0.52μM, and 129.90 ± 13.11μg/ml, respectively. The values of Λnose, however, were not correlated with the urate, ascorbate, and total protein levels.; Removing solutes from the nasal mucus using sequential saline washings in a group of 11 healthy non-smokers produced a decrease in Λ nose from an initial mean ± SE of 0.46 ± 0.03 to a value of 0.38 ± 0.03 after two sequential nasal washings and a corresponding decrease in urate levels from a mean ± SE of 13.71 ± 1.89μM to 5.61 ± 1.18μM. These sequential washings also produced an increase in ascorbate levels from a mean ± SE of 1.15 ± 0.44μM to 2.20 ± 0.65μM, and a decrease in total protein from 92.90 ± 11.12μg/ml to 64.85 ± 5.01μg/ml. In this case, the decrease in Λ nose was correlated with the decrease in urate levels (p < 0.001).; In conclusion, Λnose was modestly affected by changes in the composition of the nasal mucus, with urate being a possible target of O3 in nasal mucus. For instance, urate levels in nasal lavage were correlated with changes in O3 uptake during the nasal washing experiments. However, this relationship was not found during the day-to-day variability study. |
