Background The classic glycine receptor （GlyR） in the central nervous system is a ligand-gated membrane-spanning ion channel. Recent studies have provided evidence for the existence of GlyR in endothelial cells, renal proximal tubular cells and most leukocytes. In contrast, no evidence for GlyR in myocardial cells has been found so far. Our recent researches have showed that glycine could protect myocardial cells from the damage induced by lipopolysaccharide （LPS）. Further studies suggest that myocardial cells could contain GlyR or binding site of glycine. Methods In isolated rat heart damaged by LPS, the myocardial monophasic action potential （MAP）, the heart rate （HR） the myocardial tension and the activities of lactate dehydrogenase （LDH） from the coronary effluent were determined. The concentration of intracellular free calcium （[Ca^2＋]i） was measured in cardiomyocytes injured by LPS and by hypoxia/reoxygenation （H/R）, which excludes the possibility that reduced calcium influx because of LPS neutralized by glycine. Immunohistochemistry was used to detect the GlyR in myocardial tissue. GlyR and its subunit in the purified cultured cardiomyocytes were identified by Western blotting. Results Although significant improvement in the MAP/MAPD20, HR, and reduction in LDH release were observed in glycine ＋ LPS hearts, myocardial tension did not recover. Further studies demonstrated that glycine could prevent rat mycordial cells from LPS and hypoxia/reoxygenation injury （no endotoxin） by attenuating calcium influx. Immunohistochemistry exhibited a positive green-fluorescence signaling along the cardiac muscle fibers. Western blotting shows that the purified cultured cardiomyocytes express GlyR β subunit, but GlyR α1 subunit could not be detected. Conclusions The results suggest that glycine receptor is expressed in cardiomyocytes and participates in cytoprotection from LPS and hypoxia/reoxygenation injury. Glycine could directly activate GlyR on the cardiomyocytes and prevent calc
目的:观察甘氨酸(glycine,GLY)对缺氧/复氧离体心脏功能的影响,探讨甘氨酸对心肌缺血-再灌注(ischemia/reperfusion,I/R)损伤的防治作用及其机制。方法:利用Langendorff灌流装置复制心肌缺氧/复氧(hypoxia/reoxygenation,H/R)模型,观察不同浓度GLY处理后心脏左室收缩压(left ventricular systolic pressure,LVSP)、左室舒张末压(left ventricular end diastolic pressure,LVEDP)、左室发展压(left ventricular developed pres-sure,LVDP=LVSP-LVEDP)、左室收缩压最大上升/下降速率(the maximum rising and dropping rates of left ventricular pressure,dp/dtmaxand dp/dtmin),并在相应的时点分别测定冠脉流出液中的超氧化物歧化酶(superoxide dismutase,SOD)活性和丙二醛(malondialdehyde,MDA)的水平。结果:H/R后各时点大鼠心功能各指标均低于缺氧前;GLY处理组复氧后心功能各指标均高于H/R组,并拮抗损伤导致的SOD减少和MDA升高。结论:一定浓度的GLY能显著改善缺氧/复氧心肌的舒缩功能,其机制可能与其提高SOD活性抑制脂质过氧化反应有关。
