Abstract: and 70mg/kg fucoidin(FD,extracted from brown seaweeds Laminaria japonica aresch.) were orallyadministered separately to three groups of mice, a normal control and an experimental control were also arranged. After thefive groups of mice were fed for 15d, the three groups(LBJ group, LBP group,and an experimental control) were exposed to8.5Gyγrays and the survival rates were recorded. In other experiment, three groups of mice(fed with 10 and 40 mg/kgFD,respectively,and an experimental control) were fed for 12d. Then,the groups are exposed to 3.0Gyγ-rays. After 6d,thenumber of white blood cells(WBC) and lymphocytes(W-SCC) were counted and the lipidperoxidation level(LPO) in spleenand liver were determined. The micronucleus frequency(MF) of polychromatic erythrocytes and the sperm abberationfrequency(SF) were also observed. The results showed: the raise of the survival rates by 9.1%,and 7.1%,respectively, Thelower OF LPO levels, the protect ion of WBC and W-SCC to some extent, the decrease MF by 55.4% and 53.6% and thelower of SF by 34.9% and 30.2%, respectively. Hence,10mg/kg FD has shown remarkable radioprotective effects.

Key words: Fucoidin , Brown seaweeds , Radioprotective effect