PULMONARY SURFACTANT SUBTYPE METABOLISM IS ALTERED AFTER SHORT-TERM OZONE EXPOSURE

Rats were exposed to 0.8 ppm ozone for 2 or 12 hr. The latter conditio n resulted in lung damage and inflammation while the former did not. D irectly after exposure surfactant was isolated and two morphologically and functionally different surfactant subtypes were obtained by diffe rential centrifugation. Surfactant subtypes isolated from rats exposed to 0.8 ppm ozone for 2 and 12 hr showed an increase in the amount of heavy subtype and a decrease in light subtype. These results suggest t hat acute ozone exposure of rats can alter surfactant subtype composit ion. The conversion in vitro of heavy to light subtype was increased i n ozone-exposed rats. Degradation of surfactant protein A (SP-A) was o bserved during in vitro conversion of heavy subtype isolated from ozon e-exposed rats. This suggests that oxidation of SP-A may lead to enhan ced susceptibility for degradation. The observed effects were more pro nounced in rats exposed for 12 hr than those exposed for 2 hr, indicat ing that proteolytic enzymes from inflammatory cells may aggravate the observed effects. We conclude that extracellular surfactant metabolis m is altered by short-term exposures to ozone and that oxidation of SP -A may contribute to the observed alterations. (C) 1995 Academic Press , Inc.