[Injury of myocardial mitochondria in neonatal swines with hypoxic-ischemic brain damage].

Objective: To clarify the effect of hypoxia and ischemia on the concentration of Ca2+ in myocardial mitochondria, and on the activity of respiratory chain complex IV--cytochrome oxidase (CCO) in neonatal swines, and to find out the change of myocardial mitochondria during hypoxic-ischemic brain damage (HIBD).
Methods: The study was performed on neonatal swines. For establishment of HIBD model, the left carotid was ligated and the swine was placed under hypoxia for two hours. Then the concentration of Ca2+ and the activity of respiratory chain complex IV in myocardial cell mitochondria were measured at 0 hour and 24, 48, 72 hours after reoxygenation. The measured values from these 0-, 24-, 48-, 72-hour-HIBD-groups (n = 10 per group) and from the normal control group (n = 10) were statistically analyzed by means of ANOVA, Newman-Keuls test and linear correlation.
Results: After the swines were placed under hypoxia-ischemia for two hours, 1. the concentration of Ca2+ in myocardial mitochondria increased, till 24 hours after re-oxygenation, and then it descended at 48 hours and 72 hours after reoxygenation; 2. the activity of myocardial mitochondrial respiratory chain complex IV descended, though activity recovery was seen at 48 and 72 hours, it did not come back to normal level at 72 hours after reoxygenation; 3. the concentration of Ca2+ in myocardial mitochondria was negatively correlated with the activity of respiratory chain complex IV.
Conclusion: The results showed that in the neonatal swines with HIBD, the mitochondrial respiratory chain in myocardial cell was damaged by hypoxia-ischemia, yet it could be rehabilitated after reoxygenation. Calcium overload in myocardial mitochondria after hypoxia-ischemia might be one of the causes of the descending activity of respiratory chain complex IV.