Abstract: This experiment was aimed to study whether oyster crude polysaccharides could relieve the immune stress stimulated by LPS.Test randomly divided 30 rats into blank control group, stress control group, oyster crude polysaccharides low, medium and high dose groups.Blank control group and stress control group were fed with based diet, oyster crude polysaccharides low, medium and high dose groups were fed with based diet with 0.3%, 0.6% and 0.9% oyster crude polysaccharides.Test lasted for 28 d, the stress control group and oyster crude polysaccharides low, medium and high dose groups were intraperitoneal injected with 100 μg/kg LPS, blank control group with the same amount of saline injection, 2 h later, autopsied the rats and used relative fluorescence quantitative PCR to study the changes of the relative expression quantity of PPARγ mRNA which oyster crude polysaccharides acted on the immune stress rats.The results showed that in oyster crude polysaccharides high, medium, low dose groups and blank control group, the relative expression quantities of PPARγ mRNA in liver, spleen and lymph nodes were extremely significantly lower than that of stress control group (P<0.01), but in adrenal gland, the relative expression quantities of PPARγ mRNA of blank control group significantly decreased compared with stress control group (P<0.05).In adrenal gland and liver, there was no significant difference between oyster crude polysaccharides high and medium dose groups(P>0.05);but in spleen, there was significantly different between those two groups(P<0.05);in lymph nodes, there was extremely significantly different between those two groups(P<0.01).Adding oyster crude polysaccharides into the based diet could relieve the immunological stress from LPS, and the ease effect was better when adding amount was within the range of 0.3% to 0.6%.

Key words: oyster crude polysaccharides; immunological stress; PPARγ mRNA