G. Vansetten et G. Schultz, TRANSFORMING GROWTH-FACTOR-ALPHA IS A CONSTANT COMPONENT OF HUMAN TEAR FLUID, Graefe's archive for clinical and experimental ophthalmology, 232(9), 1994, pp. 523-526
Growth factors are known as a family of polypeptides with powerful inf
luences 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 te
ars, and ocular disease leads to decreased concentrations in tear flui
d. Using a sensitive radioimmunoassay we investigated whether TGF-alph
a is also to be considered a natural component of tear fluid and in wh
ich concentrations it occurs. All of 46 tear fluid samples from 24 vol
unteers contained TGF-alpha. The mean concentration was 161.4 pg TGF-a
lpha/ml (SD 11.6 pg). No statistically significant correlation was fou
nd between tear fluid flow and TGF-alpha concentration in the sample.
However, the concentration of TGF-alpha in tear fluid decreased signif
icantly 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 fema
les (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, l
ike EGF, a constant component of human tear fluid. The dependence of T
GF-alpha concentration on tear fluid flow and the physiological import
ance of its presence for corneal integrity and ocular surface physiolo
gy, however, require further investigation.