新生猪缺氧及复苏后心功能变化及其与心肌β1和β2肾上腺素能受体表达的关系

Relationships of cardiac compromise after hypoxic injury and expression of β1 and β2 adrenoceptors in a neonatal swine model of asphyxia

目的 探讨新生猪缺氧及复苏后心脏功能变化及心肌损伤机制. 方法 日龄l～4 d新生猪随机分为对照组（n=6）、缺氧急性期组（n=8）和缺氧亚急性期组（n=8）.对照组动物维持空气机械通气50 h;缺氧急性期组动物机械通气缺氧2h（氧浓度0.10～0.15）后空气机械通气（复苏）4h;缺氧亚急性期组缺氧2h后复苏48 h.监测缺氧处理前、缺氧2h末以及复苏过程中的血气分析、血压及血流动力学指标.复苏结束后分离左心室,采用Western印迹技术测定心肌组织β1和β2肾上腺素能受体表达,采用酶学法检测心肌组织乳酸、谷胱甘肽和氧化型谷胱甘肽含量.统计学方法采用方差分析、Tukey检验及Pearson相关分析.结果 缺氧急性期组及缺氧亚急性期组缺氧2h末pH、HCO3-和氧分压均较对照组下降（P值均＜0.05）,缺氧亚急性期组复苏后pH及HCO3-分别恢复至7.38±0.05和（23.04±2.40） mmol/L,明显高于缺氧急性期组[分别为7.25±0.07和（16.88±2.40） mmol/L]（q值分别为6.76和7.81,P值均＜0.01）,与对照组比较差异无统计学意义（P值均＞0.05）.缺氧急性期组及缺氧亚急性期组新生猪缺氧2h末平均动脉压、心输出量和每博心输出量均较对照组显著下降,而心率明显加快,差异均有统计学意义（P值均＜0.05）.复苏期间,缺氧急性期组及缺氧亚急性期组新生猪平均动脉压恢复至（42.17±6.14）和（43.19±5.55）mmHg（l mmHg=0.133 kPa）,心输出量恢复至（150.04±56.17）和（169.75±37.85） dl/min,与对照组差异无统计学意义（P值均＞0.05）.缺氧亚急性期组新生猪心肌β1和β2肾上腺素能受体表达分别为1.51±0.51和2.14±0.66,均高于对照组（分别为0.56±0.24和0.38±0.21,q值分别为7.02和10.97,P值均＜0.01）和缺氧急性期组（分别为0.65±0.20和0.45±0.11,g值分别为6.86和11.38,P值均＜0.01）.乳酸水平在缺氧急性期组和缺氧亚急性期组均高于对照组[（6.95±0.32）和（6.92±0.40）与（5.03±0.19）μmol/mg蛋白质,g值分别为15.43和15.19,P值均＜0.01].谷胱甘肽在缺氧亚急性期组低于对照组和缺氧急性期组[（352.00±16.51）与（438.35±33.66）和（464.66±52.65） nmol/mg蛋白质,q值分别为6.00和8.46,P值均＜0.01].氧化型谷胱甘肽在缺氧亚急性期组低于缺氧急性期组[（8.16±1.60）与（20.33±4.85） nmol/mg蛋白质,q=9.68,P＜0.01].缺氧亚急性期,β 1和β2肾上腺素能受体与心输出量负相关（r值分别为-0.60和-0.59,P值均＜0.05）,与每搏心输出量不相关（P值均＞0.05）. 结论 缺氧导致新生猪发生严重的代谢性酸中毒和低血压休克,复苏后可逐渐恢复正常.复苏后亚急性期心肌β1和β2肾上腺素能受体表达上调,与心脏功能受损程度有关.

Objective To investigate the hemodynamic changes and their association with the expression of β 1 and β 2 adrenoceptors after hypoxia-reoxygenation injury in a neonatal swine model of asphyxia.Methods One to four day-old piglets were randomly assigned to control group （n=6）,acute hypoxia group （n=8） and subacute hypoxia group （n=8）.The piglets in the control group were observed for 50 h under normoxic mechanical ventilation; while the acute and subacute hypoxia groups were subject to two hours of hypoxic injury induced by ventilation with 0.10-0.15 oxygen followed by 4 or 48 h of observation under normoxic mechanical ventilation,respectively.Blood gases were analyzed and the mean arterial blood pressure,heart rate,and cardiac output were recorded at different time points during the experiment.Tissues from the left ventricle were also harvested to assay lactate,glutathione and β adrenoceptors at the end of the experiment.Analysis of variance,the Tukey test and Pearson correlation analysis were used for statistical analysis of the data.Results Two hours after hypoxia,pH,HCO3-and partial pressure of oxygens （PO2） in the acute hypoxia group and subacute hypoxia group were lower than in the control group,however,pH and HCO3-in animals in the subacute hypoxia group recovered to 7.38 ± 0.05 and （23.04± 2.40）mmol/L,respectively,after reoxygenation,which was similar to those in the control group,and higher than in the acute hypoxia group [7.25±0.07 and （16.88±2.40） mmol/L,respectively,q=6.76 and 7.81,both P〈0.01].Mean arterial pressure,cardiac output and stroke volume in the acute group and subacute group were lower than those in the control animals following two hours of hypoxic injury （all P〈0.01）.After reoxygenation,the mean arterial pressure in the acute hypoxia group and subacute group recovered to （42.17±6.14） and （43.19± 5.55） mmHg （1 mmHg=0.133 kPa）,cardiac output recovered to （150.04± 56.17） and （169.75 ± 37.85） dl/min,respectively,and there were no differences compared with the control group （all P〉0.05）.Expressions of β 1 and β 2 adrenoceptors in the left ventricle in the subacute hypoxia group （1.51 ±0.51 and 2.14±0.66,respectively）,were higher than those in the control group （0.56±0.24 and 0.38±0.21,q=7.02 and 10.97,both P〈0.01） and the acute hypoxia group （0.65±0.20 and 0.45±0.11,q=6.86 and 11.38,both P〈0.01）.The lactate level in the acute hypoxia group and subacute hypoxia group was higher than that in the control group [（6.95±0.32） and （6.92±0.40） vs （5.03±0.19） μ mol/mg protein,respectively,q=15.43 and 15.19,both P〈0.01].The level of glutathione in the subacute hypoxia group was lower than the control group and acute hypoxia group [（352.00± 16.51） vs （438.35±33.66） and （464.66±52.65） nmol/mg protein,respectively,q=6.00 and 8.46,both P〈0.01）.In the subacute hypoxia group,the expressions of β 1 and β 2 adrenoceptors were negatively correlated with the changes in cardiac output （r=-0.60 and-0.59,respectively,both P〈0.05）.Conclusions Severe metabolic acidosis and cardiac dysfunction resulting from perinatal asphyxia may recover after reoxygenation,which may be associated with the enhanced expression of β adrenoceptors in the left ventricle during the subacute phase.