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

本研究旨在探讨应激（机械通气）对大鼠新生血管平滑肌的影响。孕鼠Sprague-Dawley在妊娠第21天按实验方案处理。我们采用以下两组：胎儿稳定组（fs组），由胎儿稳定治疗的新生大鼠组成。剖宫产前经胎盘经母体腹腔注射盐酸吗啡（3mg/kg）。对照组（c组）围生期不使用盐酸吗啡。两组新生儿剖宫产后均行气管插管。所有新生大鼠均予机械通气4小时。取两组患儿出生时及出生后4 h的标本，采用ELISA法测定血清肿瘤坏死因子-α (TNF-α)、白细胞介素-6 （IL-6）浓度及BALF中TNF-α浓度。右肺标本用抗小鼠TNF-α多克隆抗体免疫组织化学染色。c组出生时血清TNF-α和出生后4 h血清IL-6水平均高于fs组。出生时c组患儿BALF中TNF-α浓度趋于高于fs组。两组大鼠支气管肌层、动脉中膜及外膜均可见TNF-α阳性细胞。出生时和出生后4h， fs组的染色强度均弱于c组。我们的研究结果提示炎症细胞因子的产生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.