Maternal tobacco smoking and lung epithelium-specific proteins in amnioticfluid

The bronchiolar 16 kD Clara cell secretory protein (CC16) and the alveolar surfactant-associated protein A (SP-A) are secreted in the amniotic fluid ( A-F), where they reflect the growth and the maturity of the fetal lung. To evaluate the possible effects of in utero tobacco smoke exposure upon infan t bronchoalveolar epithelium function and maturity, CC16 and SP-A levels we re determined in AT obtained at term (36-41 wk) from 28 nonsmoking, 18 smok e-exposed, and 28 smoking mothers with uncomplicated pregnancies. Tobacco s moke exposure was assessed by questionnaire and the assay in AF and materna l urine of cotinine, a stable nicotine metabolite. The specificity of the c hanges of CC16 and SP-A concentrations in AF was assessed by comparison wit h nonpulmonary proteins of high- (albumin and transferrin) or low-molecular weight (beta (2)-microglobulin, retinol binding protein, cystatin-C). Pulm onary and nonpulmonary AF proteins were also compared by two-dimensional ge l electrophoresis between smoking and nonsmoking mothers. The levels of CC1 6 and SP-A as well as low- and high-molecular-weight proteins were not sign ificantly different between the three smoking categories. The protein patte rn of AF, established by two-dimensional gel electrophoresis, did not revea l any quantitative or qualitative difference between nonsmoking (n=10), smo ke-exposed (n=5), and smoking mothers (n=5). By multiple regression analysi s of possible determinants, tobacco smoke did not emerge as a significant p redictor of CC16 and SP-A concentrations in AF. SP-A level was dependent on ly on gestational age at birth (r(2)=0.1, p=0.001), whereas CC16 correlated only with the levels of low-molecular weight proteins (r(2)=0.2, p=0.0001) . The latter correlation suggests that CC16 enters AF not only as a result of its secretion at the surface. of the respiratory tract but also partly f ollowing its elimination by the fetal kidney. This study suggests that mate rnal smoking during pregnancy is not associated with alterations of the sec retory functions of the epithelium of the distal airways and the alveoli at term.