BIOCHEMICAL AND BIOPHYSICAL CHARACTERIZATION OF PULMONARY SURFACTANT IN RATS EXPOSED CHRONICALLY TO CIGARETTE-SMOKE

The pulmonary surfactant plays an important role in the gas exchange f unctions of the lungs. Although previous studies suggest that cigarett e smoking alters the pulmonary surfactant system in human smokers, the nature of such changes is poorly understood. The aim of the present s tudy was to determine if biochemical and biophysical properties of pul monary surfactant are affected in rats following chronic exposure to c igarette smoke. Female Sprague-Dawley rats were exposed daily to smoke from the University of Kentucky high tar/high nicotine reference ciga rettes, twice a day, for 60 weeks in a nose-only exposure system, Bloo d carboxyhemoglobin, plasma cotinine, and pulmonary aryl hydrocarbon h ydroxylase activity measurements showed that animals effectively inhal ed smoke during exposures. At termination, the bronchoalveolar lavage fluids (BALF) and the lung tissues were collected for biochemical and biophysical analyses of surfactant. The total phospholipid content of the BALF and the lung tissues from room control (RC), sham-treated (SH ), and smoke-exposed (SM) animals were the same among the different gr oups. However, disaturated phosphatidylcholine (DSPC) levels in the BA LE were significantly decreased in SM rats compared to RC or SH groups . In contrast, the lung tissue DSPC content in SM rats was not signifi cantly different from that of control groups. Phospholipid profile ana lysis of the BALE also did not reveal any significant differences amon g other major constituents of surfactant from control and SM animals, The organic extracts of BALF obtained from different animal groups wer e assessed for surface activity using a Wilhelmy balance, The results showed an increase in surface compressibility and a reduction in respr eadability index in SM group. In contrast, the stability indices of su rfactant films obtained from different groups were the same. These obs ervations suggest that decreased DSPC content in SM rats plays a role in altering the biophysical characteristics of surfactant. It is concl uded that chronic exposure to cigarette smoke adversely affects the pu lmonary surfactant system of rats. (C) 1995 society of Toxicology.