Transforming growth factor-alpha is a constant component of human tear fluid.
Growth factors are known as a family of polypeptides with powerful influences on angiogenesis, tumor growth and wound healing. Transforming growth factor-alpha (TGF-alpha) and epidermal growth factor (EGF) are structurally related peptides which bind to the same receptor, EGF-R, and also exert similar effects. EGF is a natural component of human tears, and ocular disease leads to decreased concentrations in tear fluid. Using a sensitive radioimmunoassay we investigated whether TGF-alpha is also to be considered a natural component of tear fluid and in which concentrations it occurs. All of 46 tear fluid samples from 24 volunteers contained TGF-alpha. The mean concentration was 161.4 pg TGF-alpha/ml (SD 11.6 pg). No statistically significant correlation was found between tear fluid flow and TGF-alpha concentration in the sample. However, the concentration of TGF-alpha in tear fluid decreased significantly with increasing total time of tear fluid collection (P = 0.002). TGF-alpha levels in samples collected from males (n = 16) appeared to be higher (mean 247.0 pg/ml, SD 15.3 pg/ml) than in those from females (n = 30; mean 180.0 pg/ml, SD 8.5 pg/ml; P = 0.05). No correlation was found between the age of the individuals and the concentration of TGF-alpha in their tear fluid. The findings show that TGF-alpha is, like EGF, a constant component of human tear fluid. The dependence of TGF-alpha concentration on tear fluid flow and the physiological importance of its presence for corneal integrity and ocular surface physiology, however, require further investigation.
Karolinska Institut, St. Eriks Eye Clinic, Laboratory of Dacryology, Stockholm, Sweden.
G
G
van Setten
G
G
Schultz
D000328:Adult; D005136:Eye Proteins / Q000032:analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay; D013666:Tears / Q000737:chemistry*; D016211:Transforming Growth Factor alpha / Q000032:analysis*
D005136:Eye Proteins; D016211:Transforming Growth Factor alpha; C042434:tear proteins