Detection of transforming growth factor-alpha mRNA and protein in rat lacrimal glands and characterization of transforming growth factor-alpha in human tears.
OBJECTIVE
To assess whether the lacrimal gland is a possible site of synthesis of transforming growth factor-alpha (TGF-alpha) and to characterize TGF-alpha biochemically in human tears.


METHODS
Reverse transcription-polymerase chain reaction (RT-PCR) amplification was used to analyze rat lacrimal glands for the presence of TGF-alpha mRNA. Specific monoclonal antibodies were used to localize TGF-alpha immunohistochemically in lacrimal gland tissue of rats. Human tears were analyzed for immunoreactive TGF-alpha protein using a specific radioimmunoassay, and the molecular weight of TGF-alpha in tears was characterized by Western blot analysis.


RESULTS
RT-PCR amplification of rat lacrimal gland RNA generated a band of the predicted 492 base pairs for TGF-alpha mRNA. Immunohistochemical staining of rat lacrimal gland localized TGF-alpha protein to lacrymocytes constituting acini but not to interacinar and intraacinar ducts of lacrimal glands. Western blot analysis of human tears detected a single band at MWt 16,000. Logit transformation of radioimmunoassay data for tears and TGF-alpha standard generated parallel displacement lines, indicating the presence of immunoreactive TGF-alpha levels in human tears with an average concentration of 100 +/- 20 pg/ml (mean +/- SEM).


CONCLUSIONS
Rat lacrymocytes synthesize TGF-alpha mRNA and protein, and human tears contain immunoreactive TGF-alpha, 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.
St. Eriks Eye Clinic, Karolinska Institute, Stockholm, Sweden.
G B
GB
van Setten
S
S
Macauley
M
M
Humphreys-Beher
N
N
Chegini
G
G
Schultz
D000328:Adult; D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers / Q000737:chemistry; D005136:Eye Proteins / Q000032:analysis*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007765:Lacrimal Apparatus / Q000737:chemistry*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D013666:Tears / Q000737:chemistry*; D014158:Transcription, Genetic; D016211:Transforming Growth Factor alpha / Q000032:analysis* / Q000737:chemistry / Q000235:genetics
D000911:Antibodies, Monoclonal; D017931:DNA Primers; D005136:Eye Proteins; D012333:RNA, Messenger; D016211:Transforming Growth Factor alpha; C042434:tear proteins