Chen Y Y, Xia Q
Department of Physiology, Zhejiang University School of Medicine, Hangzhou 310031, China.
Sheng Li Xue Bao. 2000 Apr;52(2):93-7.
In order to understand the intracellular mechanism of hypoxic preconditioning,we investigated the effects of G(i/o) protein, phospholipase C and adenylyl cyclase/cyclic adenosine monophosphate (cAMP) on the survival rate and lactate dehydrogenase (LDH) release of cultured neonatal rat cardiomyocytes during the reoxygenation following 3 h of hypoxia. Cardioprotection was conferred by a brief episode of hypoxia followed by reoxygenation. The obtained results are as follows: (1) Hypoxic preconditioning (25 min of hypoxia and 30 min of reoxygenation) increased the survival rate and decreased the release of LDH in the myocytes suffering from sustained hypoxia-reoxygenation. (2) Reducing the intracellular cAMP by N-ethylmaleimide, an inhibitor of adenylyl cyclase, could mimic the cardioprotection of the preconditioning. (3) Inhibition of G(i/o) protein by pertussis toxin abolished the cardioprotection of hypoxic preconditioning, with reduction of the survival rate and increase of the release of LDH. (4) U-73122 could not abolish the protective effect of hypoxic preconditioning. (5) When intracellular cAMP was increased by using 8-Br-cAMP, a high membrane permeable cAMP analogue, or forskolin, a specific adenylyl cyclase activator, the survival rate was lower and LDH activity higher than those in preconditioning myocytes. The results indicate that G(i/o) protein is a crucial component, in cardioprotection of hypoxic preconditioning in neonatal rat cardiomyocytes. Activation of phospholipase C does not seem to be involved in the intracellular signal pathway underlying the cardioprotective effect of the preconditioning.
为了了解缺氧预处理的细胞内机制，我们研究了G(i/o)蛋白、磷脂酶C和腺苷酸环化酶/环磷酸腺苷（cAMP）对缺氧3小时后复氧过程中培养的新生大鼠心肌细胞存活率和乳酸脱氢酶（LDH）释放的影响。短暂的缺氧后再复氧可赋予心肌保护作用。获得的结果如下：（1）缺氧预处理（25分钟缺氧和30分钟复氧）可提高遭受持续性缺氧-复氧的心肌细胞的存活率，并减少LDH的释放。（2）用腺苷酸环化酶抑制剂N-乙基马来酰亚胺降低细胞内cAMP可模拟预处理的心肌保护作用。（3）百日咳毒素抑制G(i/o)蛋白可消除缺氧预处理的心肌保护作用，导致存活率降低和LDH释放增加。（4）U-73122不能消除缺氧预处理的保护作用。（5）当使用高膜通透性的cAMP类似物8-溴-cAMP或特异性腺苷酸环化酶激活剂福斯可林增加细胞内cAMP时，存活率低于预处理心肌细胞，LDH活性高于预处理心肌细胞。结果表明，G(i/o)蛋白是新生大鼠心肌细胞缺氧预处理心肌保护作用的关键成分。磷脂酶C的激活似乎不参与预处理心肌保护作用的细胞内信号通路。
