Maternal exposure to environmental tobacco smoke alters Clara cell secretory protein expression in fetal rat lung.

We have previously demonstrated that aged and diluted sidestream cigarette smoke (ADSS) alters the development of bronchiolar epithelial cells in postnatal animals (C. M. Ji, C. G. Plopper, H. P. Witschi, and K. E. Pinkerton. Am. J. Respir. Cell Mol. Biol. 11: 312-320, 1994). This study was designed to examine the effects of maternal exposure to ADSS on the development of fetal Clara cells in rats with Clara cell 10-kDa protein (CC10; also designated Clara cell secretory protein) and CC10 mRNA as differentiation markers. Immunohistochemistry, Northern blots, and in situ hybridization were used to determine the abundance and distribution of CC10 at gestational days 14, 18, and 21. CC10 and CC10 mRNA were absent at gestational day 14 but were detectable at gestational day 18 and further increased by gestational day 21. Maternal exposure to ADSS was found to significantly increase fetal expression of CC10 and CC10 mRNA by gestational day 21 but not by gestational day 14 or 18. These findings demonstrate that in utero exposure to ADSS alters the normal developmental expression of CC10 in the fetal rat lung.