Abstract: Objective To explore the effect of baicalin on tumour necrosis factor-α （TNF-α） and soluble inter-cellular adhesion molecule-1 （sICAM-1） of immunosuppressed rats infected with Pneumocystis carinii. Methods Forty-nine SD rats were randomly divided into 7 groups: normal control （A）, immunosuppressed control （B）, SMZ/TMP control （C）, baicalin prevention （D）, low dose （E）, moderate dose （F） and high dose （G）. Rats of group D received six injections at three-day intervals with 3.5 mg dexamethasone sodium phosphate for 3 weeks, while groups B, C, E, F and G received same immunosuppressor but for 6 weeks. Rats in group D were given 100 mg/kg baicalin daily for 5 weeks, and groups C, E, F and G were given 250 mg/kg SMZ+50 mg/kg TMP, low dose ［100 mg/（kg?d）］, moderate dose ［200 mg/（kg?d）］, and high dose ［400 mg/（kg?d）］ baicalin daily for 2 weeks, respectively. At the end of 8th week after immunosppression, the contents of TNF-α and sICAM-1 in peripheral blood were detected by radioimmunoassay（RIA） and ELISA, respectively. The pathological change of lung was observed by lung imprint smear with gormori methenamine silver （GMS） staining and lung section with hematoxylin-eosin （HE） staining. Results The content of TNF-α in group D［（2.14±0.14） ng/ml］， group E ［（2.57±0.15） ng/ml］， group F ［（1.46±0.14） ng/ml］, group G ［（1.12±0.13） ng/ml］ andgroup C ［（1.59±0.14） ng/ml］ were higher than that of group A ［（0.70±0.21）ng/ml］（P<0.05, P<0.01）, and lower than group B ［（3.65±0.73） ng/ml］（P<0.01）. The content of sICAM-1 in group D ［（618.68±52.42） pg/ml］， group E ［（814.29±61.11） pg/ml］， group F ［（498.08±32.56） pg/ml］, group G ［（377.06±56.56） pg/ml］ and group C ［（386.95±44.98） pg/ml］ were lower than group B ［（1 247.39±288.57） pg/ml］（P<0.05）. Compared with immunosuppressed control group, there were less alveolar interstitial lymphocytes, foamy intra-alveolar exudate and inflammation of lung tissue in rats of drug treatment groups. Conclusion Baicalin can decrease the contents of TNF-α and sICAM-1， and alleviate inflammation in lung tissues of rats infected with Pneumocystis carinii.

Key words: Baicalin, Pneumocystis carinii, TNF-α, Soluble intercellular adhesion molecule-1