肾上腺髓质素对内毒素性休克大鼠心肌细胞β-肾上腺素受体激动剂反应性的影响

Effects of adrenomedullin on β-adrenergic responsiveness of cardiomyocytes in endotoxic shock rats

目的:研究肾上腺髓质素(ADM)对内毒素性休克大鼠心肌细胞β-肾上腺素受体激动剂反应性的影响。方法:成年SD大鼠腹腔注射脂多糖(LPS 10 mg/kg)4 h后,分离心室肌细胞。用细胞缩短的方法观察ADM对心肌收缩的影响。以细胞内cAMP的水平为指标,研究ADM对内毒素性休克大鼠心肌细胞β-肾上腺素受体激动剂反应性的影响。结果:休克心肌细胞细胞缩短程度较正常心肌细胞明显减弱。ADM孵育心肌细胞时间超过60min具有明显的负性肌力作用。特异性ADM受体拮抗剂ADM-(22-52)可取消上述两种负性肌力作用。休克心肌细胞cAMP基础水平较正常心肌细胞降低(P<0.05)。与正常对照组比较,用1μmol/L异丙肾上腺素(Iso)刺激内毒素性休克大鼠的β-肾上腺素受体,cAMP的增加明显减少(P<0.01)。1μmol/L forskolin[一种直接的腺苷酸环化酶(AC)激动剂]增加cAMP的作用在2组间没有显著变化(P>0.05)。ADM-(22-52)可使内毒素性休克时心肌细胞对β-肾上腺素受体激动剂降低的反应性得到恢复。结论:内毒素性休克时过量产生的ADM使大鼠心肌细胞收缩减弱,有可能是ADM使大鼠心肌细胞对β-肾上腺素受体刺激的反应性降低所致。

AIM：To study the effects of adrenomedullin（ADM） on β-adrenergic responsiveness of the cardiomyocytes in endotoxic shock rats.METHODS： Ventricular myocytes were isolated from adult rats 4 h after intraperitoneal injection of lipopolysaccharide（LPS,10 mg/kg）.The contraction of the cardiomyocytes was determined by the method of measuring the cell shortening.The content of intracellular cAMP was detected by ELISA.RESULTS： ADM with prolonged incubation（〉1 h） showed negative inotropic effect on the cardiomyocytes and was specifically inhibited by its antagonist ADM-（22-52）.Compared with the control cells,a significant decrease in the cell shortening was observed in shock cardiomyocytes.ADM-（22-52） reversed this decreased cell shortening in shock cells and also reversed the negative inotropic effect of ADM on the cardiomyocytes.The basal cAMP content in shock cardiomyocytes was lower than that in the control cells（P〈0.05）.Treatment with isoprenaline at a concentration of 1 μmol/L increased the cAMP content in the normal cardiomyocytes more than that in the shock cardiomyocytes（P〈0.01）.Treatment with ADM-（22-52） restored the responsiveness of β-adrenergic receptor in the shock cells.Treatment with forskolin at a concentration of 1 μmol/L increased the content of cAMP both in the normal cardiomyocytes and in the shock cardiomyocytes to the same levels（P〉0.05）.CONCLUSION： The β-adrenergic responsiveness of the myocytes is reduced in endotoxic shock rats.ADM-（22-52） reverses the hyporesponsiveness,suggesting a positive contribution of ADM to this process and a role of ADM in the pathogenesis of sepsis.