| [Background] :Techniques of deep hypothermic circulatory arrest (DHCA) and deep hypothermic low flow (DHLF) have been widely applied on cardiac surgery, but it's temporarily or permanent complications were high to 4%-25% (average 8%), and safe time of operation only 45-60 minutes, which limited its clinical application. Presently, some studies showed that complications of DHCA are correlated to neuron apoptosis. To detect effects on apoptosis of cortex neuron in DHCA rats, the rat model of occluding bilateral common carotid artery in the deep hypothermic (21C) rats had been established, and flow cytometry, TUNEL, electron microscope, immunohistochemistry (SABC) and RT-PCR had been studied.[Methods]: part I: To establish a new rat model of cerebral ischemia/protect during DHCA: 20 SD rats were used in the experiment, little animal respirator was to assist anesthetized rat's respiration after tracheal cannula, artery press through artery spile in femoral artery, electrocardiograph, temperature, blood saturation of O2 (SaO2) and arterial blood gases were monitored during the whole experiment, blood flow of bilateral common carotid artery of rat were occluded about 60 minute when its temperature was reduced to 21 C by ice, then normal temperature was resumed. Neurological deficits were judged by Longa's criterion after 4 hours and 24 hours.Part II: Effect of DHCA on neuron apoptosis of rats: Thirty rats were divided randomly into three groups: deep hypothermic control group(DHC), normal temperature control(NTC) group and DKCA group, model of bilateral hemispheric cerebral ischemia/ reperfusion injury were prepared by 60min occlusion followed 24h of reperfusion of bilateral common carotid artery in the deep hypothermia (21C). (1) Cerebral cortexes were removed and then dissociated, measured with flow cytometer analyze cell apoptosis, the morphological changes were examined by electron microscope. (2) Measured cell apoptosis of cerebral cortexes with TUNEL. (3) detected expressions of Bcl-2, Bax and Caspase-3 proteins with the technique of immunohistochemistry.Part III: Effect of DHCA on expression of correlative gene of neuron apoptosis. Detected expressions of mRNA of Bcl-2, Bax and Caspase-3 with technique of RT-PCR, and measured rates of density of PCR Products.Data were analyzed by software SPSS 11.5[Results]: (1) In experimental group: four rats failed of resuscitation, sixteen survived, and the mortality rate was 20%. There were no severe neurological deficits (Grade 1-2 of 4) after 24 hours. In control group, there were no deaths of rats during experiment, and no neurological deficits after 4 hours.(2) measured neuron apoptosis of Cerebral cortexes were increased with flow cytometry the rate of apoptosis of the DHC group, the NTC group and the DHCA group were (2.20 + 0.43) %, (19.23 + 1.01) % and(4.72 + 1.02)% respectively (P<0.01 ).(3)detected apoptosis and its correlative proteins of Cerebral cortexes with TUNEL and immunohistochemistry respectively: The level of Bcl-2 protein expressions (65.13 + 1.84)% and the ratio of Bcl-2/Bax were significantly higher in DHCA group than NTC group ( P<0.01 ), the level of Bax protein expressions ( 2.87 + 0.87 ) %, rate of apoptosis cell ( 4.35 + 0.58 ) % and Caspase-3 protein (3.36+0.92)% were significantly lower in DHCA group than NTC group ( P<0.01).(4) The mRNA expressions of NTCgroup, DHC group and DHCA group: Bcl-2 were (39.7 +12.1) %, (13.9 + 8.5) % and (69.3 +8.9) % (P<0.001) respectively. Bax were (49.3+12.2) %, (7.2+3.1) % and (20.6+4.5) % (P<0.001) respectively. Bcl-2/Bax were 3.36 + 1.98, 1.93 + 0.85 and 0.81 + 0.91 respectively (P<0.01). The mRNA expressions of Bcl-2 were significantly higher in DHCA group then the others, but the mRNA expressions of Bax and Caspase-3 in NTC group were significantly higher then the others.[Conclusion]: Deep hypothermia can reinforce tolerance of Anoxic neuron, accelerated expressions of Bcl-2 gene, inhibit expressions of Bax and Caspase-3, and decreased and inhibited cell apoptosis, although it couldn't prev...
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