Relationships of cardiac compromise after hypoxic injury and expression of β1 and β2 adrenoceptors in a neonatal swine model of asphyxia / 中华围产医学杂志

ABSTRACT

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.