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

Before the experiment, all male SD rats were fasted overnight (8 h), with free access to water. The "two-hit" ALI animal model induced by hemorrhagic shock/resuscitation and LPS instillation 24 was used in this study. The rats were randomly divided into six groups: Sham, ALI model and prednisone (70 mg/kg) groups, as well as CHCP groups of 25, 50 and 100 mg/kg. All animals were anesthetized with 1 g/kg urethane (i.p.). The right common carotid artery was cannulated with a 24-gauge Angiocath indwelling needle filled with 0.4% heparin for the monitor of mean arterial pressure (MAP), blood sampling and resuscitation. The heparinization was performed by injecting 0.1 mL 0.4% heparin through the angiocath to prevent clotting. Hemorrhagic shock was initiated by blood withdrawal, leading to a reduction of the MAP to 4075 mmHg in 20 min. This blood pressure was maintained by further blood withdrawal if MAP was higher than 45 mmHg and by infusion of 0.5 mL normal saline (NS) if the MAP was less than 35 mmHg. After a hypotensive period of 60 min, rats were resuscitated by transfusion of the withdrawn blood in 1 h. Then, either LPS (1 mg/kg in 200 μL NS) or NS alone was administered intratracheally (i.t.). CHCP (100 mg/kg, 50 mg/kg and 25 mg/kg, dissolved in saline) was given intragastrically (i.g.) at 30 min before the LPS instillation. The rats of the positive control group received a single dose of prednisone 70 mg/kg i.p. Sham animals underwent the same surgical procedures but without the hypotensive process, and received intratracheal instillation of NS. Serum samples of all animals were obtained from the right carotid artery at 0, 2 and 4 h after the administration of LPS. All animals were breathing spontaneously during the experiment and sacrificed at 4 h after LPS administration.