EPIDERMAL GROWTH FACTOR-LIKE MOLECULAR-SPECIES IN NORMAL BRONCHOALVEOLAR LAVAGE FLUID

Normal bronchoalveolar lavage fluid (BALF) contains mitogenic activity for fibroblasts and type 2 pneumocytes. A number of growth factors th at might contribute to this activity have been identified in BALF. We found that a molecule or molecules able to bind to epidermal growth fa ctor (EGF) receptors on mouse lung fibroblasts were present in normal mouse BALF and could be blocked by an antiserum to mouse EGF. Receptor binding was partially blocked by preincubation with heparin, indicati ng a relationship to the heparin-binding subgroup of EGF-like growth f actors. Heparin markedly enhanced the mitogenic activity of BALF for f ibroblasts, but we were unable to establish whether the EGF-like molec ule contributed to this activity. Immunoblotting using the anti-EGF se rum identified a protein of M(r) 88,000 in concentrated BALF. The cell ular source and physiological role of this growth factor merit further investigation.