OBJECTIVETo observe the effects of three different doses of polydatin (PD) on pulmonary interstitial fibrosis in rats induced by bleomycin.

METHODOne hundred and twenty-nine healthy Sprague-Dawley rats three months old, were randomly divided into six groups. Group A: normal control group; group B: model group treated with bleomycin (pretreatment with saline 1 mL x kg(-1) intraperitoneally before bleomycin); group C: PD 10 mg x kg(-1) (pretreatment with PD 10 mg x kg(-1) intraperitoneally before bleomycin); group D: PD 20 mg x kg(-1) (pretreatment with PD 20 mg x kg(-1) intraperitoneally before bleomycin); group E: PD 40 mg x kg(-1) (pretreatment with PD 40 mg x kg(-1) intraperitoneally before bleomycin), group F: dexamethason (DXM) treated group (pretreatment with saline 1 mL x kg(-1) intraperitoneally before bleomycin and then with DXM 1 mg x kg(-1) x d(-1)). At day 3, 7, 14, 28 after injection of bleomycin, eight rats in each group were randomly chosen to be killed. The right lungs of dead rats were removed and appropriately processed for hematoxylin and eosin (H&E) stain, histologically observed under light microscope. The hydroxyproline content and the PLA2 activity in pulmonary homogenate were measured with alkaline hydrolysis assay and acid modified microtitrimetic method. The levels of leukotriene C4 (LTC4), prostaglandin E2 (PGE2), transforming growth factor-beta1 (TGF-beta1) in bronchoalveolar lavage fluid (BALF) were measured with enzyme-linked immunosorbent assay (ELISA).

RESULTAt day 3, 7, 14, 28 after intratracheal instillation of bleomycin in rats of group B, the PLA2 activity in lung homogenate and the levels of its metabolic products PGE2, LTC4 as well as TGF-beta1 in BALF increased significantly compared with those in group A (P < 0.01). And lung hydroxyproline concentration began to grow up markedly at day 7 compared with those in group A (P < 0.05), reaching its maximum at day 28. Compared with group B, three different doses of PD and DXM significantly reduced the activity of the PLA2 and hydroxyproline concentration in lung homogenate as well as the levels of PGE2, LTC4, TGF-beta1 in BALF at various periods (P < 0.05). There was statistically significant difference between three different doses of PD groups (P < 0.05). And the group E (PD 40 mg x kg(-1)) was lower than group D (PD 20 mg x kg(-1)), group D was lower than group C (PD 10 mg x kg(-1)) (respectively, P < 0.01). Group E and DXM group were no significant difference. However, all these observation parameters were higher than the normal level (compared with group A, P < 0.01). Histological studies revealed that it was showed less inflammation and a lower degree of fibrosis in the lungs treated with PD than bleomycin model group.

CONCLUSIONPD has the protective effect on pulmonary interstitial fibrosis. However, it can't completely block the process of pulmonary fibrosis.