Effects of transforming growth factor-beta on collagen synthesis by fetal rat lung epithelial cells

Studies were performed to characterize the effects of acute and chronic exposure to transforming growth factor-beta (TGF-beta) on collagen biosynthesis by fetal rat lung epithelial (FRLE) cells, a cell line established from the fetal rat lung alveolar epithelial cell. Neither condition of exposure to TGF-beta stimulated cell growth, but both conditions increased total protein synthesis. Quantitative evaluation by carboxymethyl-Trisacryl chromatography revealed that FRLE cells synthesized types I, III, IV, and V collagen under all circumstances. Acute and chronic exposure to TGF-beta increased total collagen production approximately 50% and 300%, respectively, with the increases in total collagen production exceeding those of total protein synthesis. In addition, these analyses indicated that the production of types I and III molecules was stimulated to a greater extent than was the synthesis of types IV and V molecules. Both experimental conditions increased the ratio of secreted to cell-associated molecules for types I and III molecules, decreased this ratio for type IV collagen, but minimally affected the culture distribution of type V collagen. Additionally, both conditions of exposure to TGF-beta were found to increase the proportion of the homotrimeric forms of types I and V molecules relative to their heterotrimeric counterparts. Thus, these studies establish that TGF-beta selectively and type-specifically alters collagen production without affecting growth in an epithelial cell line of fetal rat lung origin.