| OBJECTIVES: To observe the effects of normothermic cardiopulmonary bypass (CPB) on neuronal apoptosis and brain-derived neurotrophic factor (BDNF) mRNA expressions in hippocampi of rats, establishing a rat model of CPB.METHODS: Twenty adult male Sprague-Dawley (SD) rats were randomly divided into CPB group (n=10) and Sham group (n=10). All animals were anesthetized (350mg·kg-1 of chloraldurat for intramuscular), orally intubated, and mechanically ventilated. The right atrium was cannulated via the right superior vena and the tail artery was cannulated. The systemic anticogulation was achieved with heparin(500U·kg-1). The animals seleted for CPB group underwent normothermic (37.8℃～38.7℃) CPB at a flow of (120～150)mL·kg-1·min-1 for 60 minutes, with the blood drained from the right cave- atrium and infused into the tail artery. Sham group underwent all the same operations except for CPB. During the procedure, body temperature (T) and haemodynamical parameters were monitored, while arterial blood gas, electrolytes and hemodilution parameters were analyzed. 2 hours after CPB in CPB group or 3 hours after operation in Sham group, the animals were killed and hippocampi were removed, the left hippocampi preserved in nitrogen canister for the detection of BDNF mRNA, while the right ones preserved in 4% polymerized formaldthyde for the examination with electron microscope. Hippocampal BDNF mRNA expressions were determined with reverse transcriptase polymerase chain reaction (RT-PCR) method.RESULTS: 1. All animals survived during the whole process. There were no significant difference in base-values of the physiological parameters between both groups (P>0.05), also in body-temperature (T), heart rate (HR) and electrolytes (Na+, K+, iCa2+) at every time point observed. Mean arterial pressure (MAP), central venous pressure (CVP), arterial partial pressure of carbon dioxide (PaCO2),arterial partial pressure of oxygen (PaO2), hematocrit (Hct) and haemoglobin levels (Hb) of CPB group changed significantly comparing to those of Sham group (P<0.05), showing that MAP decreased, CVP increased, PaCO2 increased, PaO2 decreased, Hct and Hb decreased, and these were consistent with the changes of clinical CPB. 2. Electron microscopy showed that hippocampal neurons of Sham group were nearly normal, mitochondrial form was normal, mitochondria cristae was visible, rough surfaced endoplasmic reticulum was plentiful and ribosomes sticked in it, but some vascular endothelial cells were swollen. Hippocampal neurons of CPB group were swollen or occurred apoptosis, nuclear membrane fractured or disappeared, nucleuses of neurons occurred karyopyknosis or vacuole zone, autosomes in nucleuses disappeared, cytoplasmic organoids in cytoplast decreased or disappeared, mitochondria or rough surfaced endoplasmic reticulum dissolved, and vascular endothelial cells were obviously swollen. 3. In the electropherogran of RT-PCR product, the electrophoresis strips of CPB group were brighter and clearer than those of Sham group. The calculation of gelatum image analytical system showed that the bdnf /β-actin ratio in CPB group was siganificantly higher than that in Sham group (P<0.05), suggesting that hippocampal BDNF mRNA expressions in CPB group was higher than that in Sham group.CONCLUSIONS: 1. The model of closed chest cardiopulmonary bypass in rats is an ideal model for the research correlated with CPB. 2. Normothermic CPB can induce injury to hippocampus in rats. 3. Normothermic CPB can induce hippocampal BDNF mRNA expressions in rats. 4. On the condition of normothermic cardiopulmonary bypass, the increasement of BDNF mRNA in hippocampus can not effectively prevent the hippocampal injury from CPB, may be related to the factors such as the inadequate and delayed effect of BDNF expressions. |
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