尾吊大鼠股动脉中ERK1/2含量变化及对收缩功能的影响

Changes of ERK1/2 in Femoral Arteries of Tail-suspended Rats and Their Effects on Contractility

目的研究细胞外信号调节激酶 (ERK1 /2 )在尾吊大鼠股动脉中含量的变化及其对收缩功能的影响。方法采用 1 4d尾部悬吊大鼠模型模拟微重力效应 ,利用离体血管环灌流技术 ,在无抑制剂存在或分别给予α1 受体拮抗剂哌唑嗪 ( prazosin)及丝裂原活化蛋白激酶的激酶 (MEK)抑制剂PD980 5 9后 ,检测大鼠股动脉对去甲肾上腺素的反应性变化 ;用Western免疫印迹 -增强型化学发光系统 (ECL)检测基础状态下ERK1 /2的总含量及无抑制剂存在或分别给予哌唑嗪、PD980 5 9后 ,NE诱导的ERK1 /2磷酸化程度 ,并与对照组相比。结果与对照组相比 ,尾部悬吊 1 4d后 ,大鼠股动脉对NE的最大收缩反应明显下降 ;PD980 5 9可明显抑制对照组和悬吊组大鼠股动脉由NE诱导的最大收缩反应 ,且对照组的抑制效应明显大于悬吊组 ;哌唑嗪导致对照组和悬吊组大鼠股动脉对NE的量 -效反应曲线右移 ,但由Schild公式计算所得的PA2 值显示受体敏感性在两组间无显著差异。尾吊 1 4d恢复 7d后 ,大鼠股动脉对NE的收缩反应与同步对照组相比无显著差异。Western免疫印迹结果表明 ,与对照组相比 ,悬吊 1 4d后基础状态下大鼠股动脉中ERK1 /2的总含量高于对照组 ,但磷酸化程度却低于对照组 ;经NE作用后 ,ERK1 /2磷酸化程度仍低于对照组。恢复 7d后 ,ERK1

Objective To study changes of extracellular signal regulated kinase 1 and 2 (ERK1/2) in femoral arteries of tail suspended rats and their effects on contractility. Method Microgravity was simulated by elevating the hindquarters of Wistar rats to produce hindlimb unweighting(HU). In the absence or presence of prazosin and PD98059 respectively, isometric tension of vessel rings from femoral arteries in response to norepinephrine(NE) was determined by in vitro perfusion technique; Basal total ERK1/2 level and phosphorylated ERK1/2 level stimulated by norepinephrine in the absence or presence of prazosin and PD98059 respectively were detected by Western blotting enhanced chemically lightening system. Result The maximal contractile response to NE was significantly lower in femoral arterial rings from 14day HU rats as compared with those in control rats. PD98059 caused a marked inhibition of NE induced maximum contractile response in both control and HU femoral arterial rings. Moreover, the effect of inhibition was more significant in control rats than that in HU rats. Prazosin caused a right shift of the concentration response curves(CRCs) to NE in both control and HU rats, but no difference was found between the two groups for the PA 2 of prazosin calculated by Schild analysis, which showed that the sensitivity of α 1 adrenoceptor was not changed by HU. After 7d recovery, the difference of contractile response of femoral arterial rings to NE between recovered group and control group was nonsignificant. Data from Western blotting showed that basal total ERK1/2 levels were elevated in femoral arterial rings from 14d HU rats as compared with those in control rats, but the levels of basal and NE stimulated phosphorylated ERK1/2 were higher in control as compared with HU rats. After 7d recovery, the basal total ERK1/2 level and phosphorylated ERK1/2 level were not different from control. Conclusion Microgravity simulated by 14d HU can induce abnormality of MAPK/ERK pathway, which may contribute to declined contractile response of femoral vessel rings to NE.