Expression of TGF-alpha, EGF, and EGF receptor in fetal rat lung

To define the distribution of transforming growth factor-alpha (TGF-alpha) and its relationship to epidermal growth factor (EGF) and EGF receptor in lung development and to determine whether epithelial cells produce TGF-alpha, we studied the expression of TGF-alpha, EGF, and their receptor in late-gestation fetal rat lung and in cultured fetal rat lung cells. TGF-alpha, EGF, and EGF receptor were colocalized in epithelial and smooth muscle cells of bronchioles and bronchi and in epithelial 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 EGF receptor mRNA, but no detectable TGF-alpha mRNA. These results demonstrate fetal lung epithelial cells are a source for TGF-alpha and suggest that TGF-alpha might act through an autocrine or paracrine mechanism with epithelial and mesenchymal cells. The colocalization of TGF-alpha and EGF suggests that these growth factors might act in parallel in lung development.