Tear proteins of normal young Hong Kong Chinese

Background: Analysis of tear proteins is of diagnostic value for abnormal ocular conditions such as dry eye syndrome. Many studies of tear proteins have been performed on Caucasian subjects. However, little is known about these proteins in Chinese eyes. Methods: The total tear protein concentrations of 30 normal young Hong Kong Chinese were determined by the Bradford method and the modified Lowry method. Bovine serum albumin (BSA) and bovine immunoglobulin G (IgG) were both used as standards for each method. The tear protein 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, using 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 respectively. The mean±SD concentrations of major tear proteins were 2.73±0.82 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 lysozyme. Conclusion: The results of total tear protein concentrations indicated that values obtained from different methods and different standards were not comparable. The tear protein patterns of our subjects were qualitatively similar to those reported for Caucasian subjects. However, the concentrations 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.