Beneficial effects of Houttuynia cordata polysaccharides on “two-hit” acute lung injury and endotoxic fever in rats associated with anti-complementary activities

Lu, Yan; Jiang, Yun; Ling, Lijun; Zhang, Yunyi; Li, Hong; Chen, Daofeng

2.6. Fever experiment 2.6.1. Model and grouping Adult male Wistar rats (200-230 g) were housed at least 3 days before experiments under room temperature at 1872°C, relative humidity at 55%-60% and a 12-h light-dark cycle. The rectal temperature was determined twice every day. On the day before experiments, each two rats were housed in one cage, fasted for 10 h with free access to water. The rats with stable baseline temperatures were selected for experiment by determining their rectal temperature three times every 20 min, and divided into six groups (n ¼ 6): sham group, LPS-induced model group, CHCP (at different doses of 50, 100, and 200 mg/kg) groups, and aspirin (150 mg/kg) group. The drugs were diluted in normal saline for oral administration. After drug administration for 30 min, LPS (60 μg/kg) was injected intraperitoneally (i.p.) to induce fever. The same volume saline (1 mL/kg) without LPS was injected in the sham group. The body temperature was recorded every 30 min from 0 to 6 h after LPS injection. The change of body temperature was calculated as ΔT. The thermal response index (TRI,°C × h) of each group was evaluated as the area under the temperature-time curve, which was calculated by summing the area of the trapezoids under every two data points. The area of each trapezoid from t i to t iþ1 under the curve was calculated as (t iþ1 -t i ) × (ΔT i þΔT iþ1 )/2. After the rats were anesthetized with 1 g/kg urethane i.p., the serum and blood samples were collected for complement activity assay and leukocyte counts, respectively.