EXPRESSION OF TGF-ALPHA, EGF, AND EGF RECEPTOR IN FETAL-RAT LUNG

To define the distribution of transforming growth factor-alpha (TGF-al pha) and its relationship to epidermal growth factor (EGF) and EGF rec eptor in lung development and to determine whether epithelial cells pr oduce TGF-alpha, we studied the expression of TGF-alpha, EGF, and thei r receptor in late-gestation fetal rat lung and in cultured fetal rat lung cells. TGF-alpha, EGF, and EGF receptor were colocalized in epith elial and smooth muscle cells of bronchioles and bronchi and in epithe lial cells of saccules. Epithelial cells cultured from late-gestation fetal rat lung transcribe TGF-alpha and EGF receptor mRNA and produce TGF-alpha and EGF receptor proteins. Cultured fibroblasts contained EG F receptor mRNA, but no detectable TGF-alpha mRNA. These results demon strate fetal lung epithelial cells are a source for TGF-alpha and sugg est that TGF-alpha might act through an autocrine or paracrine mechani sm with epithelial and mesenchymal cells. The colocalization of TGF-al pha and EGF suggests that these growth factors might act in parallel i n lung development.