Effects of various body temperatures after intratracheal lipopolysaccharide‐induced acute lung injury in rats

Abstract

STUDY OBJECTIVES In this study, we determined the effects of various body temperatures (BTs) after initiation of lipopolysaccharide (LPS)-induced lung injury. METHODS Forty-nine, adult, male, Sprague-Dawley rats each weighing 300 to 400 g were used. The treated rats were challenged with intraperitoneal administration of 5 mg/kg LPS. Control animals received IP saline solution injections. After 16 h, animals were anesthetized and received direct intratracheal (IT) injection of LPS (1 mg/0.2 mL) or saline solution (control animals). A cooling or heating blanket was then used to control BT for 5 h. The rats were randomly assigned to three control groups of mild hypothermia (34° C), normothermia (37° C), and mild hyperthermia (39° C), and three LPS groups of various temperature control. BAL was done in the left lung 5 h after the IT injection of LPS. Parts of the right lung were excised for myeloperoxidase and malondialdehyde measurements, whereas the rest was collected for wet/dry (W/D) ratio determination. RESULTS LPS caused significantly increased W/D ratio, LDH activities, protein concentrations, and tumor necrosis factor-α concentrations in BAL fluid, and MPO activities and MDA levels in lung tissues. The pathologic picture also showed increased neutrophil infiltration in lung tissues. In contrast, treatment with mild hypothermia, but not hyperthermia, significantly attenuated these parameters of lung injury induced by LPS. CONCLUSIONS Mild hypothermia applied after initiation of acute lung injury induced by LPS in rats had a protective effect by inhibiting the inflammatory reaction.