Changes of febrile response and placental pathological inflammation in pregnant rats after intrauterine infection in late gestation / 中华围产医学杂志

ABSTRACT

Objective To explore the febrile response and placental pathological inflammation of pregnant rats exposed to intrauterine infection in late gestation.Methods Pregnant Sprague-Dawley rats at gestational day 18 were randomly divided into control group and intrauterine-infected group with six rats in each.The intrauterine-infected group was intraperitoneally injected with 350 μ g/kg lipopolysaccharide to establish a rat model of intrauterine infection,while the control group was injected with sterile saline of the same dose.Core temperature was measured every 1 h after intraperitoneal injection of lipopolysaccharide or saline for 8 h.At gestational day 19,after anesthesia,the placentas were taken and stained with HE.The expression levels of tumor necrosis factor-α,interleukin-6,and interleukin-1β in the placenta were determined by enzyme linked immunosorbent assay.Student t test was used for statistical analysis.Results (1) There was no temperature difference between the two groups before experimental treatment (P ＞ 0.05).Core temperature was increased 1 h after the lipopolysaccharide injection,reaching (37.67 ±0.08) ℃.The increase of temperature was significant compared with the control group [(37.13 ± 0.08) ℃,t=10.178,P ＜ 0.01].Fever was lowered 2 h later and the rats became hypothermic with body temperature below 37 ℃ in the intrauterine-infected group.The body temperature in the intrauterine-infected group after 2-6 h was (37.70 ± 0.10),(37.23 ± 0.05),(36.57 ± 0.06),(36.60 ± 0.10) and (36.57 ± 0.08) ℃,respectively,compared with the control group [(36.83 ±0.12),(36.63 ± 0.12),(36.71 ± 0.07),(36.87±0.12),and (36.77±0.08) ℃,respectively],the differences being all statistically significant (t=11.402,11.163,-4.025,-4.000 and-4.243,all P ＜ 0.01).(2) HE staining revealed large amounts of neutrophils infiltration,vascular enlargement and congestion in the placenta of the intrauterine-infected rats.No inflammatory cell infiltration was observed in the control placentas.(3) The expression levels of proinflammatory cytokine tumor necrosis factor-α [(0.62 ± 0.02) ng/g],interleukin-6 [(66.12 ± 5.11) ng/g],and interleukin-1β [(7.09± 1.23) ng/g] in the intrauterine-infected group were higher than those in the control group [(0.27±0.01),(16.71 ±1.55) and (2.86 ± 0.38) ng/g,respectively].The differences were all statistically significant (t=-26.608,-18.749 and-5.714,all P ＜ 0.01).Conclusion After exposure to lipopolysaccharide in late gestation,pregnant rats show significant inflammatory response in the placenta,with suppression of febrile response and presence of hypothermia.