Abstract: AIM: To investigate the effect of semen plantaginis(SP)on [Ca²⁺]_i, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP)of lens epithelial cell (LEC)damaged by H₂O₂ and the mechanism of calcium signal transduction.METHODS: Sub-cultured bovine LECs were incubated with H₂O₂ and deferent concentrations of SP(8, 4, 2mg/mL)for 12, 24 and 36 h respectively.The LEC activities were observed by methyl thiazolyl tetrazolium assay (MTT).LEC [Ca²⁺]_i were detected by spectrofluorophotometer.Intracellular cAMP and cGMP of LEC were determined by radioimmunoassay.And the effects of different concentrations of SP and incubation for different times of 12, 24, 36 h were studied.RESULTS: The activities of LEC increased in deferent concentrations of SP groups compared with those in H₂O₂ group(P<0.01), which showed dosedependent and time-dependent manner.The [Ca²⁺]_i of LEC decreased in SP groups compared with those in H₂O₂ group(P<0.01), which showed time-dependent manner.The cAMP concentration of LEC decreased and the cGMP concentration of LEC increased in SP groups compared with those in H₂O₂ group (P< 0.01), which showed time-dependent manner.CONCLUSION: SP can protect LEC against oxidative damages and increase activities of LEC.The [Ca²⁺]_i, cAMP and cGMP signal transduction system and the cross-talk may be the mechanisms of SP preventing and delaying the cataract formation.

Key words: semen plantaginis, lens, epithelial cell, oxidative damage, corpuscular signal transduction