Expression Of MCTs In The Central Nervous System Of Rat And The Role Of MCTs In Hypoxic-Ischemic Brain Injury

Objective: To investigate the distribution of monocarboxylatetransporters (MCTs) in the normal rat brain and ischemic injured rat brain,so as to explore the role of MCTs as brain energy metabolism duringhypoxic-ischemic brain injury and the mechanism of MCTs expressionregulation.Methods: A total of192healthy male adult SD rats were randomlydivided into sham operation group and Middle Cerebral ArteryOcclusion(MCAO) groups and nomal grope．The operation procedures inthe sham operation group were as same as those in the ischemic group butwithout occluding unilateral MCA．In this study, the distribution of MCTsin the brain of normal rats was investigated by Nissl’s staining,immunohistochemistry (IHC) and immunofluorescence (IF). The brainswere taken out at interval times of1h、3h、6h、12h and24h, respectively.Subsequently, TTC staining, HE staining, immunohistochemistry, doubleimmunofluorescence and Western blot were used to detect the expression ofMCTs in different cell types.Results: MCT1and MCT4-possitive cells were widely distributed in the cortex, striatum, hippocampus, corpus callosum, hypothalamus, brainstem but scattered in other parts of brain. At the cellular level, MCT1andMCT4-possitive cells were mainly located in the ependymal cells, choroidplexus, astrocytes and few neurons. Besides, MCT1was strongly expressedin endothelial cells also. MCT2-possitive cells were observed in theolfactory bulb, telencephalon, diencephalon, cerebellum and brain stem. TheMCT2were widely and uniformly in the olfactory bulb, telencephalon anddiencephalon. In the brain stem, MCT2was distributed in the visceral motornuclei and somatic sensory nuclei except general visceral motor and sensorynuclei. In addition, MCT2was expressed in the nuclei of non-cranial nerves,such as nucleus ceruleus, inferior olive nucleus, raphe nucleus,gigantocellular reticular nucleus, intermediate reticular nucleus and lateralreticular nucleus, etc. Besides, MCT2-possitive cells were observed in thelateral cerebellar nucleus, interposed cerebellar nucleus, medial cerebellumnucleus. MCT-possitive cells had different forms in different regions.Expression of MCT1,2,4was no significant difference in the shamgroup compared with and normal group. The results of IHC and IF showedthat the expression of MCT1,2,4were increased in the injured sidecompared with sham controls since MCAo3h. With the extension ofischemia time, the immunological activity for MCT1,2,4was increased inthe ischemic side, especially in the hypothalamus, and reached the peak at24h. MCT-positive cells were mainly branched in shape, Western Blot showed that the expression of MCT1,2,4were increased in the injured sidesince MCAo3h and reached the peak at24h.Conclusions:(1) The result revealed that MCT1,2,4is not evenly distributed inall the regions of the brain, suggests that MCT1,2,4have somespecial important roles in maintaining some of essential life activitiesunder physiological conditions.(2) The increase of MCTs in the injured side may correspond to theenergy metabolism function. MCTs could transporte lactate fromastrocytes to the neurons, for neuronal energy consumption andprotection.