[Effects of liposome-entrapped E. coli endotoxin on lung pathophysiology in rats]

The effects of repeated intravenous injections of E. coli endotoxin (ETX)-containing liposomes (LP) on the development of emphysematous change in rats were examined. Male Wistar rats, weighting 150-200 g, were divided into 3 groups. Group 1; rats treated with phosphate buffered saline (PBS), Group 2; rats treated with liposome-entrapped PBS, Group 3; rats treated with liposome-entrapped ETX (10 mg/ml). In each group, 0.5 ml was injected intravenously once a week for 8 consecutive weeks. After 8 weeks, functional and morphometrical analyses of lungs were performed. Functional residual capacity (FRC), total lung capacity (TLC), and static compliance (Cst.) were measured using a pressure plethysmograph for small animals. Mean linear intercept (MLI) and internal surface area (ISA) were also determined. TLC did not differ among the 3 groups. In rats treated with liposome-entrapped ETX, Cst. corrected by body weight (Cst./body weight) was significantly increased compared with that in liposome-entrapped PBS-treated rats. Further more, MLI was larger than that of the other 2 groups and ISA was less than that of the liposome-entrapped PBS-treated rats. These results suggest that liposome-entrapped ETX induces emphysematous changes in rats.