Effects of prolonged methylprednisolone treatment after pulse therapy for paraquat-intoxicated rats.

Abstract

This study was designed to evaluate prolonged methylprednisolone (MP) treatment after pulse therapy for paraquat (PQ)-intoxicated rats. Acute PQ toxicity was induced by intraperitoneally injecting single toxic dose of 25 mg/kg of body weight. Rats were divided into four groups: control group (saline solution for 15 days), PQ group (saline solution for 15 days after PQ toxicity), pulse group (15 mg·kg-1·day-1 MP for 3 days after PQ toxicity and then saline solution for 12 days) and pulse + prolonged group (15 mg·kg-1·day-1 MP for 3 days after PQ toxicity; dosage was subsequently reduced by half every 2 days, and MP was terminated until 0.47 mg·kg-1·day-1). Hydroxyproline (HYP) content in lung tissues was evaluated through enzyme-linked immunosorbent assay, and lung fibrosis was examined using a semiquantitative scoring system (Ashcroft staging criteria). Lung wet-to-dry weight (W/Dc) ratio and 15-day survival rates of the rats were also analysed. Similar survival rates (55.0 vs. 65.0%) were obtained for the pulse group and the pulse + prolonged group. The W/Dc (4.79 ± 0.42 vs. 5.29 ± 0.35), HYP content in the lung tissues (3.23 ± 0.24 vs. 3.72 ± 0.23 μg/mg) and lung fibrosis scores (2.69 ± 0.74 vs. 3.12 ± 0.60) of the pulse + prolonged group were lower than those of the pulse group. Prolonged MP treatment after pulse therapy could effectively ameliorate PQ-intoxicated acute lung injury in rats. However, further studies should be performed to verify our findings.