THE INTERVENTION EFFECT OF SELENIUM ON DECREASE OF CATHEPSIN B,D ACTIVITIES OF THYROID FOLLICULAR EPITHELIAL CELL LINE INDUCED BY IODINE EXCESS

Objective: To detect the damage of excessive iodine on the activities and mRNA of cathepsin B and D and observe the effects of selenium intervention. Method: Thyroid follicular epithelial cell line FRTL was cultured in Kaighn’s modified Ham’s F-12 medium. ① The cells were divided into 8 groups for detection of activities of cathepsin B and D (CB and CD). The medium of NI group did not contain selenium or iodine, while EI group contained 50 mmol/L KI, and IS group contained 50mmol/L KI and different dosages of 0.1,0.2,0.5,1.0,2.0 and 5.0 μmol/L selenium (sodium selenite). ②The mRNA levels of cathepsin B and D were detected by real-time PCR. The medium of NI group and EI group was same as above, but IS group only contained 0.1μmol/L selenium besides 50mmol/L KI. Results: The activities of CB decreased in EI group (50mmol/L KI treated 12 h), while CD decreased after 24 h and both activities were improved in IS groups with 0.1~0.5μmol/L selenium. The mRNA levels of CB and CD in EI group decreased, while in IS group were improved. Conclusion: Excessive iodine resulted in goiter through decreased levels of activities and mRNA of CB and CD. The intervention of selenium on goiter mayinduce its amelioration effect on decrease of CB and CD activities and the optimal dosage ranges from 0.1μmol/L to 0.5μmol/L.