The purpose of this work is to measure the pharmacokinetic parameters of r-Sak in rats as well as the biodistribution and the excretion of r-Sak in rats. 125 I-r-Sak was applied for the purpose. The results showed that the pharmacokinetics of 125 I-r-Sak following intravenous injection with two doses (70μg/kg and 840μg/kg) in rats was in correspondence with 2-compartment-model. The T 1/2(α) were 5.47±2.13 and 8.45±4.50min and T 1/2(β) were 96.15±22.29 and 58.78±32.79min for the two dose groups. AUC were 0.895±0.455 and 38.36±5.181μg·min·mL -1 . There were no marked differences of T 1/2(α) and T 1/2(β) between the two dose groups ( P >0.05)

but the AUC increased markedly with the dose increase ( P <0.05). The biodistribution of 125 I-r-Sak was wide in rats. Radioactivity was highest in kidney

followed in order by plasma

liver

lung

spleen

heart and brain. Excretion experiment showed that the sum of the accumulative excretion of the radio-material plus the enrichment of the radio-material in thyroid was approximately 80% in 96h.