Quantiative Analysis And Ultrastructural Observation Of Mitochondria In Hippocampal Neurons Of Rats Under Whole Body Deep Hypothermic Circulatory Arrest

Objective To investigate the protective effects of deep hypothermia at subcellular level by quantitative analysis and ultrastructural observation on hippocampal mitochondrion of rats under whole body deep hypothermic circulatory arrest.Methods Thirty-three Sprague-Dawley (SD) rats were divided randomly into three groups:deep hypothermic circulatory arrest (DHCA) group, normal temperature circulatory arrest (NTCA) group and normal control (NC) group. The animal model of closed-chest cardiopulmonary bypass (CPB) was established in SD rats by means of external cannulation. In DHCA group,circulatory arrest were performed in the deep hypothermia (<20℃), the time was 10min; in NTCA group, circulatory arrest were performed in normal temperature(36.8℃～37℃), the time was 10min; in NC group without circulatory arrest and deep hypothermia, the time was 10min; The hippocampus was taken at the end of each course to observe its ultrastructure by electro microscope. Meanwhile the circumference, the diameter, the mean gray scale, the shaped index, the volume density (Vv), the numerical density (Nv), the mean volume and the specific surface (8) of mitochondria were also measured. Data were analyzed by software SPSS11.5.Results The ultrastructure of the mitochondria was normal in NC group; the mitochondria had a slight clearance swelling (especially in cristae), but without breaking and the structure was still complete in DHCA group compare with NC group; the ultrastructural changes of the mitochondria in DTCA group were obvious, including the mitochondria were swollen, the cristae were twisted, reduced even dispeared, the outer membraneand the inner membrane were broken, wolly masses with high density and vague border appeared in some mitochondria. There was significent difference in the two dimension parameters of circumference, diameter and mean gray scale of mitochondria among the three groups (F=144.67,129.54,13.28,p< 0.05). What's more, the circumference and the diameter of mitochondria presented the trend NTCA group>DHCA group>NC group(P<0.05), except shaped index, which did not show significent difference among the three groups (F=2.35,P>0.05). Stereology results:the difference among the three groups at vacuolar mitochondrion was observed to reveal significance in Vv, Nv, V andδ. There was significent difference in Vv, Nv, V andδamong the three groups (F=41.307,105187.6,12543.02, 459.472, P<0.05)and presented the trend NC group>DHCA group>NTCA group (P<0.05) in Vv, Nv and 8, except V presented NC group<DHCA group<NTCA group(P<0.05).Conclusion The swelling of mitochondria can be observed in hippocampal CA1 pyramidal neurons of SD rats under circulatory arrest. After comparing the results of DHCA group and NTCA group on the same condition, we found deep hypothermia can greatly reduce the degree of mitochondria swelling. We hypotheses that deep hypothermia could have the protective effects to mitochondria while ischemia, which would be one of the mechanisms in protective effects of deep hypothermia.