DETECTION OF TRANSFORMING GROWTH-FACTOR-ALPHA MESSENGER-RNA AND PROTEIN IN RAT LACRIMAL GLANDS AND CHARACTERIZATION OF TRANSFORMING GROWTH-FACTOR-ALPHA IN HUMAN TEARS

Purpose. To assess whether the lacrimal gland is a possible site of sy nthesis of transforming growth factor-alpha (TGF-alpha) and to charact erize TFG-alpha biochemically in human tears, Methods. Reverse transcr iption-polymerase chain reaction (RT-PCR) amplification was used to an alyze rat lacrimal glands for the presence of TGF-alpha mRNA. Specific monoclonal antibodies were used to localize TGF-alpha immunohistochem ically in lacrimal gland tissue of rats. Human tears were analyzed for immunoreactive TGF-alpha protein using a specific radioimmunoassay, a nd the molecular weight of TGF-alpha in tears was characterized by Wes tern blot analysis. Results. RT-PCR amplification of rat lacrimal glan d RNA generated a band of the predicted 492 base pairs for TGF-alpha m RNA. Immunohistochemical staining of rat lacrimal gland localized TGF- alpha protein to lacrymocytes constituting acini but not to interacina r and intraacinar ducts of lacrimal glands. Western blot analysis of h uman tears detected a single hand at MWt 16,000. Legit transformation of radioimmunoassay data for tears and TGF-alpha standard generated pa rallel displacement lines, indicating the presence of immunoreactive T GF-alpha levels in human tears with an average concentration of 100 +/ - 20 pg/ml (mean +/- SEM). Conclusions. Rat lacrymocytes synthesize TG F-alpha mRNA and protein, and human tears contain immunoreactive TGF-a lpha, suggesting that the lacrimal gland may be an exocrine source for TGF-alpha in tears. The single MWt 16,000 form of TGF-alpha in human tears appears to be generated by an unusual proteolytically processing of the pro-TGF-alpha transmembrane precursor protein.