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J Appl Physiol 73: 1939-1945, 1992;
8750-7587/92 $5.00
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Journal of Applied Physiology, Vol 73, Issue 5 1939-1945, Copyright © 1992 by American Physiological Society

ARTICLES

Kinetics of NO2 air space absorption in isolated rat lungs

E. M. Postlethwait, S. D. Langford and A. Bidani
Department of Internal Medicine, University of Texas Medical Branch, Galveston 77555-0876.

We previously showed, during quasi-steady-state exposures, that the rate of inhaled NO2 uptake displays reaction-mediated characteristics (J. Appl. Physiol. 68: 594-603, 1990). In vitro kinetic studies of pulmonary epithelial lining fluid (ELF) demonstrated that NO2 interfacial transfer into ELF exhibits first-order kinetics with respect to NO2, attains [NO2]-dependent rate saturation, and is aqueous substrate dependent (J. Appl. Physiol. 71: 1502-1510, 1991). We have extended these observations by evaluating the kinetics of NO2 gas phase disappearance in isolated ventilating rat lungs. Transient exposures (2-3/lung at 25 degrees C) employed rebreathing (NO2-air) from a non-compliant continuously stirred closed chamber. We observed that 1) NO2 uptake rate is independent of exposure period, 2) NO2 gas phase disappearance exhibited first-order kinetics [initial rate (r*) saturation occurred when [NO2] > 11 ppm], 3) the mean effective rate constant (k*) for NO2 gas phase disappearance ([NO2] < or = 11 ppm, tidal volume = 2.3 ml, functional residual capacity = 4 ml, ventilation frequency = 50/min) was 83 +/- 5 ml/min, 4) with [NO2] < or = 11 ppm, k* and r* were proportional to tidal volume, and 5) NO2 fractional uptakes were constant across [NO2] (< or = 11 ppm) and tidal volumes but exceeded quasi-steady-state observations. Preliminary data indicate that this divergence may be related to the inspired PCO2. These results suggest that NO2 reactive uptake within rebreathing isolated lungs follows first-order kinetics and displays initial rate saturation, similar to isolated ELF.(ABSTRACT TRUNCATED AT 250 WORDS)


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L. W. Velsor and E. M. Postlethwait
NO2-induced generation of extracellular reactive oxygen is mediated by epithelial lining layer antioxidants
Am J Physiol Lung Cell Mol Physiol, December 1, 1997; 273(6): L1265 - L1275.
[Abstract] [Full Text] [PDF]


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