In order to study the changes of heatstress protein 70（HSP70） and nitric oxide synthase（NOS） immunity histochemistry in spleen and liver of rats in the stages of recovery after heat stress,42 SD male rats of 6 months old were randomly divided into two groups,namely control group and heat stress group.The control group were in the heat stress environment for 1 h then 6 stages of recovery in 0-48 h which were recorded.The results showed that：（1） The expression of HSP70 in rats spleen reached peak after 4 h,with a large number of cells rupture.After 8 h,the trend of the expression gradually decreased,but there were significant differences between the 5 stages of recovery in 0-12 h and the control group（P0.01）.After 48 h,there was no significant difference between control group and heat stress group（P0.05）;（2） In the liver,the positive expression of HSP70 in heat stress group and the control group was no significant difference（P0.05）;（3） The rates of NOS expression in rat liver cytoplasm reached peak after 8 h,with the positive expression in the vascular endothelial cells,and then gradually declining,but there were significant differences between the 5 stages of recovery in 0-12 h and the control group（P0.01）.In the stage of 48 h,there was no significant difference between control group and heat stress group（P0.05）;（4） NOS expression in spleen was not obvious either heat stress group or control group.[著者文摘]