Alveolar surfactant is known to be impaired after inhalation of various oxidizing agents (NO2, ozone) as well as in inflammatory lung processes, in which leucocyte-derived active oxygen species or arachidonic acid oxygenation products may be involved. The effect of lipid peroxidation, oxygen-free radicals and oxygenated versus native arachidonic acid on the surface tension behaviour of natural surfactant was tested in vitro. The studies were performed on pooled surfactant material, obtained from bronchoalveolar lavage of rabbit lungs, in a Langmuir trough/Wilhelmy balance system. Initiation of lipid peroxidation with FeCl3/ascorbate or UV radiation and the generation of OH.(FeCl2/EDTA/H2O2), O2-. (xanthine/xanthine oxidase) and 1O2 (NaOCl/H2O2) provoked a common profile of changes: delayed reduction of surface tension during compression with an increase in minimal compressibility accelerated decrease of film pressure during expansion, reduction of hysteresis area and markedly augmented monolayer collapse rate. Addition of arachidonic acid resulted in decreased minimal compressibility, stability index and hysteresis area. Incubation with the arachidonic acid cyclooxygenase products, prostaglandin E2, I2, F2 alpha or thromboxane B2, with soybean lipoxygenase or with H2O2 and O2-exposure caused only moderate or no alteration of surfactant behaviour in vitro.
Conclusion: oxidative stress, but not arachidonic acid oxygenation products, provoked altered surface tension behaviour of natural surfactant in vitro.