Intrauterine endotoxin infusion in rat pregnancy induces preterm delivery and increases placental prostaglandin F2α metabolite levels

Objective: This study was designed to examine the effects of intrauterine endotoxin (lipopolysaccharide) on rat pregnancy. Study Design: Pregnant Sprague-Dawley rats (N = 26) were implanted with uterine catheters on day 15 or 16 of a 22-day gestation. Animals were randomly assigned to receive either lipopolysaccharide (25 or 50 μg) or sodium chloride solution (1 mL) on day 17 and then were either sacrificed on day 19 or observed until delivery. Placentas were harvested at the time of death, homogenates were prepared, and prostaglandin F_2α metabolite levels were determined by means of radioimmunoassay. Data were analyzed by analysis of variance, Student-Newman-Keuls, and Mann-Whitney tests. Results: Lipopolysaccharide-treated groups (25 and 50 μg) displayed a shorter interval to delivery (mean ± SE, 82 ± 13 and 63 ± 8 hours, respectively) than control animals (117 ± 3 hours). Pups of lipopolysaccharide-treated (25 and 50 μg) female animals had lower live birth weights (4.92 ± 0.01 and 5.12 ± 0.24 g, respectively) compared with control animals (6.04 ± 0.07 g). Placental homogenates from lipopolysaccharide-treated female animals contained higher levels of prostaglandin F_2α metabolite (1567 ± 64 and 1475 ± 59 pg/mL) than those from sodium chloride solution–infused control animals (804 ± 68 pg/mL). Conclusion: Bacterial products induce the preterm delivery of low-birth-weight pups in rats, possibly by increasing local prostaglandin biosynthesis. (Am J Obstet Gynecol 2000;182:1496-501.)