Background: Analysis of tear proteins is of diagnostic value for abnormal o
cular conditions such as dry eye syndrome. Many studies of tear proteins ha
ve been performed on Caucasian subjects. However, little is known about the
se proteins in Chinese eyes. Methods: The total tear protein concentrations
of 30 normal young Hong Kong Chinese were determined by the Bradford metho
d and the modified Lowry method. Bovine serum albumin (BSA) and bovine immu
noglobulin G (IgG) were both used as standards for each method. The tear pr
otein patterns were determined by sodium dodecyl sulfate-polyacrylamide gel
electrophoresis (SDS-PAGE), and the concentrations of major tear proteins
were quantified by scanning densitometry after SDS-PAGE. Results: The mean/-SD total tear protein concentrations determined by the Bradford method, u
sing BSA and IgG as standards, were 6.05+/-1.58 mg/ml and 11.48+/- 2.32 mg/
ml respectively. The values determined by the modified Lowry method, using
the same two standards, were 9.66+/-2.03 mg/ml and 7.53+/-1.80 mg/ml respec
tively. The mean+/-SD concentrations of major tear proteins were 2.73+/-0.8
2 mg/ml for lactoferrin, 0.021+/-0.028 mg/ml for human serum albumin, 2.89/- 0.88 mg/ml for tear-specific prealbumin and 2.46+/-0.44 mg/ml for lysozy
me. Conclusion: The results of total tear protein concentrations indicated
that values obtained from different methods and different standards were no
t comparable. The tear protein patterns of our subjects were qualitatively
similar to those reported for Caucasian subjects. However, the concentratio
ns of the major proteins of our subjects were not in accordance with those
reported previously. The main reason may be the large variability of method
used.