Production of transforming growth factor (TGF) beta by fetal lung cells.

TGF beta is supposed to play an important role in the process of epithelial maturation in the developing fetal lung. Using an immunofluorescence approach, we showed that fetal rat lung fibroblasts elaborate the three TGF beta isoforms known in mammals (TGF beta 1, beta 2 and beta 3) whereas epithelial cells appear to synthesize only TGF beta 1 and beta 3. Isolated fibroblasts secrete the three isoforms. Biological assay of TGF beta activity in fibroblast-conditioned media did not reveal significant changes according to the stage when fibroblasts were isolated.