A. Ben-jebria et al., Kinetics of protein depletion in rat bronchoalveolar lavage fluid following in vitro exposure to nitrogen dioxide, ENV TOX PH, 6(3), 1998, pp. 177-185
Upon inhalation, nitrogen dioxide (NO2), a strong oxidizing agent, first co
mes into contact and reacts with the fluids lining the airways of the respi
ratory tract. These respiratory tract lining fluids (RTLF) form a barrier b
etween the inhaled toxic pollutant and the epithelium which protects the un
derlying tissue from inflammation. Proteins, mainly albumin, and antioxidan
ts are the major components of the RTLF. Many studies have utilized human b
lood plasma to study the interaction of an extracellular fluid with ozone.
In this study, we used bronchoalveolar lavage fluids (BALF) as a more speci
fic surrogate for rat RTLF, and we utilized the native fluorescence as a ma
rker to investigate the depletion kinetics of naturally-occurring protein f
ollowing exposure to NO2 in a controlled flow reactor system. We also studi
ed the depletion kinetics of albumin in a buffered salt solution. The resul
ts indicated that: (1) the decay in fluorescence was linearly dependent on
the concentration of NO2, indicating that protein oxidation was first order
with respect to NO2 concentration in both BALF and in buffered albumin sol
ution; (2) the depletion kinetics of protein in BALF was non-linear with re
spect to substrate concentration; (3) the rate of protein depletion was muc
h slower in BALF than in a buffered solution of albumin, suggesting that th
e presence of antioxidants in BALF protected proteins from being oxidized b
y NO2; and (4) whereas the addition of ascorbic acid to buffered albumin so
lution significantly attenuated albumin depletion, the addition of glutathi
one had no effect. This suggested that the reaction rate constant of ascorb
ic acid was considerably higher than that of glutathione. (C) 1998 Elsevier
Science B.V. All rights reserved.