Protective Effect Of Sodium Bicarbonate On The Brain Against Ischemia-reperfusion Injury In Rats

Objective: To investigate the protective effect of sodium bicarbonate on the brain against ischemia-reperfusion (I/R) in rats and the underlying mechanism.Methods: Forty-eight male Sprague-Dawley rats weighing 310-350g(supplying from the centre of experimental animal of Hebei Medicine university) were randomly divided into 4 groups(n=12/group).The model of cerebral ischemia /reperfusion injury in rats was induced by occlusion of bilateral common carotid arteries and basilar artery for 10 min and then reopening them. Group S: sham operating group, bilateral common carotid arteries and basilar artery were not occluded. Group I/R: ischemia–reperfusion group, three vessels were occluded for 10 min and then reopening them for 8 h. Group N(sodium bicarbonate + I/R group) and group Na (0.9%NaCl + I/R group): at the beginning of reperfusion the rats were intravenously either sodium bicarbonate 2.5mg/kg or an equal volume of 0.9% NaCl. And to collect the microdialysis fluid in every rat. The perfusion rate was 2μl/min and one tube of fluid was collected for each 10 min. Beginning at 10 min before occlusion(T1),collection time was 1 hour (the train isT2,T3,T4,T5,T6 in turn).Rats were tested the open fild test (OFT) and the inclined plane test (IPT) at 8 hours after reperfusion and then executed. The cortex of frontal lobe of the right brain were removed for light microscopic examation of the change of pathology, the other tissue of the right brain for electron microscopic examation and the left brain for the brain water content.Results: 1. The contration of lactateCompared with group S, the concentration of Lac in groupN, I/R and Na was significantly lower than that in brain ( P < 0.05). The Lac in group I/R were much higher than that in group Nand Na (p<0.05). Compared with group Na, it was low in groupN. There were significant differences among them.2. The brain water contentGroup S: the brain water content was74.96%, Group I/R: the brain water content was 83 .11%, Group Na : the brain water content was 81.72%, Group N: the brain water content was79.16%.the increase in cortex water content was in the order: group I/R>groupNa>group N>group S (p<0.05). There are significant differences among them.3. Pathology of light microscopeGroup S: The morphosis of nerve cells was nearly whole The cytoplasma was plentiful and had been thin dyed. The nucleolus was clear.Group I/R: Most of the nerve cells were wizened and the dyeing aggravated. The nucleolus was unclear. The boundary between the cytoplasma and the nucleolus was not pure, while the nucleolus was unclear.Group Na: Parts of the nerver cells were crinkly. The boundary between the cytoplasma and the nucleolus was not pure, while the nucleolus was unclear.GroupN: N part of the never cells were wrinkly, but the structur was approximately normal. Karyon was elliptic and nucleolus was clear.4. Pathology of transmission electron microscopeGroup S: The morphosis of nerve cells was almost intact. A little of critae and membrane of mitochondrium were amalgamation or lost. The rough endoplasmic reticulms had little the phenomenon of degranulation. The Golgi's complex was normal and had some secondary lysosomes and free ribosome.Group I/R: The cytoplasm was extremely dropsical and the count of organelles decreased. The count of organelle was significantly decreasing. The most of critae and membrane of mitochondrium were fused or lost. And the phenomenon of degranulation was very serious in rough endoplasmic reticulms. The Golgi's complex was not quite whole and there were some free ribosomes.Group Na : The cytoplasm was extremely dropsical and the count of organelles decreased. The count of organelle was significantly decreasing. The most of critae and membrane of mitochondrium were fused or lost. And the phenomenon of degranulation was very serious in rough endoplasmic reticulms. The Golgi's complex was not quite whole and there were some free ribosomes but the secondary lysosomes were reduced.GroupN: The morphosis of nerve cells was normal on the whole. The cytoplasm was little dropsical. A part of critae and membrane of mitochondrium were fused or lost. And the phenomenon of degranulation was very light in rough endoplasmic reticulms. The Golgi's complex was almost whole. There were some secondary lysosomes and free ribosomes.5. The grade of neuroethologyOFT: Compared with group I/R, the grade of neuroethology in group S, N, and Na was significantly higher (P<0.05) than that of group I/R. Compared with group Na, it was higher in group N and S (P<0.05). There was not significant difference between groupN and S (P>0.05).IPT: Compared with group S, the grade of neuroethology in group I/R and Na was lower(P<0.05), while there was not significant difference between group Na and I/R (P>0.05). It was higher in group I/R than in groupN (P<0.05).6. Microdialysis Determination of the concentration of lactate Each time the comparison: sham-operated group there was no significant difference (P> 0.05), the remaining three groups, compared with T1,T2~T6 lactic acid concentrations increased (P <0.05), with the extension of time a downward trend. Comparison groups: T1, T2, the differences among the three groups (P> 0.05), T3~T6, the lactate concentration were: sham-operated group