AIM:To investigate the protective effect of E-64d on calcium-induced cataract and its possible mechanism.

METHODS: Sixteen paired rabbit lens were randomly divide into two groups, the lens of any pair of one was as experimental group, the other for the control group. Experimental group contained concentration of 5, 10, 15, 20, 25, 30, 35, 40mmol/L CaCl₂ 1 640 culture medium, the control group contained 1 640 culture medium, the situation was observed by turbidity after 36h. Twenty-four paired rabbits lens were randomly divided into two groups, the lens of any pair of one was as experimental group, the other for the control group. Experimental group contained CaCl₂(5～30mmol/L)+ E-64d of 1 640 culture medium and control group containd CaCl₂(5～30mmol/L)of 1 640 culture medium. Lens transparency and relative gray values were detected, Atomic absorption spectrophotometer was used to detect lens calcium(Ca^{2 +})content. The data were analyzed with SPSS 13.0 statistical software. Measurement data were expressed (-overx)±s and the differences of two groups were compared by pared- samples t test. P<0.05 was considered statistically significant.

RESULTS: Transparent lens opacity occurred in medium containing CaCl₂, and with the Ca²⁺ concentration increased, degree of lens opacity was also improved. When Ca²⁺ concentration >30mmol/L, black cross line below the lens was hardly seen through in culture medium, and lens cortex was almost completely cloudy. Lens opacity incubated with 1 640 mediun containing E-64d was declined compared with controls. There were significant difference of relative gray scale between experimental group and control group(t=3.820, P=0.001<0.01). However, experimental group and control group had no significant effect on Ca²⁺ uptake by lens(t=2.144, P=0.055>0.05).

CONCLUSION: The high levels of extralenticular calcium can induced cataract. E-64d, an inhibitor of calpain, can inhibit calcium-induced lens opacity, However, E-64d has no significant effect on Ca²⁺ uptake by lens. Its inhibitory effect on lens opacification may be due to a direct action on the activity of calpain. Moreover, maybe it can inhibit degeneration of crystallin or apoptosis and necrosis of epithelial cell by other approaches to delay the occurrence of cataract.