Determination of low-molecular-mass antioxidant concentrations in human respiratory tract lining fluids

Antioxidants present within lung epithelial lining fluids (ELFs) constitute an initial line of defense against inhaled environmental oxidants such as ozone, nitrogen oxides, and tobacco smoke, but the antioxidant composition of human ELFs is still incompletely characterized. We analyzed ELF concentr ations of the low-molecular-mass antioxidants ascorbate, urate, glutathione (GSH), and alpha-tocopherol by obtaining bronchoalveolar lavage (BAL) and nasal lavage fluids from healthy nonsmoking volunteers and compared two dif ferent BAL procedures. ELF dilution by the lavage procedures was estimated by measurement of urea in recovered BAL fluids in comparison with those in blood plasma from the same subjects. The results indicated that a recently developed, single-cycle BAL procedure minimizes influx of non-ELF urea into the instilled fluid and thus allows for a more accurate determination of E LF antioxidant concentrations. Using this procedure, we determined that bro nchoalveolar ELF contains 40 +/- 18 (SD) mu M ascorbate, 207 +/- 167 mu M u rate, 109 +/- 64 mu M GSH, and 0.7 +/- 0.3 mu M alpha-tocopherol (n = 12 su bjects). Similar analysis of nasal lavage fluid yielded nasal ELF levels of 28 +/- 19 mu M ascorbate and 225 +/- 105 mu M urate (n = 12 subjects), whe reas GSH was undetectable (<0.5 FIM). Our results demonstrate that ascorbat e and urate are major low-molecular-mass ELF antioxidants in both the upper and lower respiratory tract, whereas GSH is present at significant concent rations only in bronchoalveolar ELF.