TGF-ALPHA PROTEIN AND RECEPTOR LOCALIZATION IN LARYNGOTRACHEAL TISSUE

Both normal cell turnover and healing of laryngeal and tracheal injuri es involve cell migration and mitosis. The proteins that regulate norm al cell turnover and wound healing in the larynx and trachea have not been established. It is possible that peptide growth factors, such as transforming growth factor-alpha (TGF alpha) acting through its recept or (EGF/TGF alpha-R), participate in the regulation of these processes . To investigate this hypothesis. we analyzed laryngotracheal cells fo r TGF alpha protein and receptor in normal and postwounding conditions . TGF alpha protein was detected by immunohistochemical analysis in no rmal ferret laryngeal and tracheal mucosa. Specific binding to the EGF /TGF alpha receptor in membrane homogenates of ferret larynx and trach ea reached saturation after 60 minutes at 37 degrees C, and was effect ively displaced by unlabeled epidermal growth factor (EGF) or TGF alph a, but not by unlabeled insulin, angiotensin II, or basic fibroblast g rowth factor. Scatchard analysis of the specific binding indicated the presence of high-affinity (Kd = 117 pmol) and low-affinity (Kd = 40 n mol) binding sites. The maximum number of available binding sites was 73 fmol/mg protein. Localization of the EGF/TGF alpha receptor by auto radiographic analysis of I-125-EGF binding to sections of normal ferre t larynx and trachea revealed EGF/TGF alpha receptors throughout the e pithelium, with the highest grain density in the basal layers. Quantit ive analysis of autoradiographic grain density between normal, intubat ed, and extubated animals revealed no significant differences. The pre sence of TGF alpha protein and its receptor in normal and wounded lary nx and trachea supports the hypothesis that these proteins are involve d in regulating physiologic responses of laryngotracheal cells.