Research for the effect of vaso-activators in neonatal vascular smooth muscle

本研究的目的是利用大鼠模型阐明应激(机械通气)对新生血管平滑肌的影响。妊娠21d的SD大鼠按实验方案进行处理。我们使用以下两组：胎儿稳定组(FS-group)，由经胎儿稳定化处理的新生大鼠组成。在剖宫产前经胎盘注射盐酸吗啡(3 mg/kg)。对照组(C组)围产期不注射盐酸吗啡。两组新生儿剖宫产术后均行气管插管。所有新生大鼠均在机械通气下管理4h。分别于出生时和出生后4h采血，用双抗体夹心法测定血清肿瘤坏死因子-α(TN-α)、白介素6(IL-6)和肺泡灌洗液中肿瘤坏死因子-α的浓度。取右肺标本，用抗小鼠肿瘤坏死因子α多克隆抗体进行免疫组织化学染色。C组出生时血清肿瘤坏死因子-α和出生后4h血清IL-6水平均高于FS组。出生时C组大鼠肺泡灌洗液中肿瘤坏死因子-α浓度明显高于FS组。两组大鼠支气管肌层、动脉中层及外膜均可见肿瘤坏死因子-α阳性细胞。在出生时和出生后4小时，FS组的染色强度均弱于C组。我们的结果提示，对炎性细胞因子产生的调节可能调节血管平滑肌的活动。

The aim of this study is to elucidate the effect of stress (mechanical ventilation) in neonatal vascular smooth muscle using a rat model. Pregnant Sprague-Dawley rats were treated by experimental protocols on day 21 of gestation. We used the following two groups : The fetal stabilization group (FS-group) which consisted of neonatal rats treated by fetal stabilization. They received morphine hydrochloride (3mg/kg) via the placenta by means of maternal intra-abdominal injection before undergoing a caesarean section. In the control group (C-group), they received no morphine hydrochloride during the perinatal period. Tracheal intubations were performed in neonates after caesarean section in both groups. All neonatal rats were managed under mechanical ventilation for 4 hours. We collected the samples at birth and at 4 hours after birth in both groups and then measured the serum Tumor-necrosis-factor-alpha (TNF-α), Interleukin-6 (IL-6) concentrations and the TNF-α concentration in BALF by ELISA. The specimens obtained from the right lung were immunohistochemically stained with anti-mouse TNF-α polyclonal antibody. The levels of serum TNF-α at birth and IL-6 at 4 hours after birth in the C-group increased, in comparison to that in the FS-group. At birth in the C-group, the TNF-α concentration in BALF tended to be higher than that in the FS-group. TNF-α positive cells were identified in the bronchial muscular layers, arterial media and externa in both groups. The staining intensity in the FS-group was weaker than that in the C-group both at birth and at 4 hours after birth. Our result suggests that the regulation of the production of inflammatory cytokines may regulate the action of vascular smooth muscle.