Objective: To evaluate the prevention and treatment action of Shashen Maidong decoction and thus explore the possible mechanisms. Method: One hundred forty-one SD rats were randomly divided into five groups

control group

model group

Shashen Maidong decoction 10.3 g·kg-1 prevention group

Shashen Maidong decoction 10.3 g·kg-1 treatment group

and dexamethasone 10.4 mg·kg-1 treatment group. The rats model of radiation pneumonitis was established by exposeing rats to the chest X-ray except control group. The prevention group was given Shashen Maidong decoction one week before modeling

while the corresponding drug solutions of other four groups were administrated from the second day after modeling respectively once per day. Rats were anesthetized by intraperitoneal injecting 10% chloral hydrate. The blood was collected. The levels of plasma interleukin-6(IL-6)

transforming growth factor-β1(TGF-β1) and tumour necrosis factor-α(TNF-α) were measured by ELISA at 2

4

6 weeks seperately after modeling. Result: Compared with control group

IL-6

TGF-β1 and TNF-α increased in model group (P<0.01) at 2

4

6 weeks. Compared with model group

the levels of serum IL-6

TGF-β1

TNF-α in Shashen Maidong decoction prevention group

Shashen Maidong decoction group and dexamethasone treatment group were significantly lowered (P<0.01

or P<0.05). The levels of IL-6

TGF-β1

TNF-α in Shashen Maidong decoction prevention group were lower than Shashen Maidong decoction group and dexamethasone treatment group (P<0.01)

and in dexamethasone treatment group which was higher than that of Shashen Maidong decoction treatment group (P<0.01). Conclusion: The Shashen Maidong decoction may inhibit the inflammation of alveolar and improve the process of pulmonary fibrosis in radiation peumonitis by reducing the levels of IL-6

TGF-β1

TNF-α.