The Study On Cold Adaptation Of Tree Shrews

The studies of the adaptive thermogenic capacity and mechanisms of small mammals in cold were one of the hottest issues in ecophysiology, and had gone deeply the molecular level. The uncoupling protein (UCP) played an important role in the adaptive thermogenesis of animals. And it also tightly associated with energy allocating and utilizing and human's adiposity and NIDDM.Tree shrew (Tupaia belangeri), which was the representative tropic and sub-tropic small mammal distributed in the south of China, had studied on cold adaptive characters of genie level in cold stress as the experimental animal in our research. This study would help to probe into adaptive thermogenic mechanism, survival mechanism and evolution strategy of small mammals at low temperature. The study also offered the substantial basis to the cure of adiposity and diabetes which not tying on insulin.This thesis consisted of four parts: 1. The effects of different p-AR agonist selectivity on the thermogenic capacity of tree shrews; 2. The effects of cold exposure on mitochondrial respiration of liver in tree shrews; 3. The effects of cold exposure on total RNA in liver and BAT of tree shrews; 4. The RT-PCR of UCP 1 and UCP2 and the sequencing of UCP 1 of tree shrews.The detailed results and conclusions were as follow as:1. Compared with control (out of cold exposure), the RMR of tree shrews after cold exposure increased, the Pa-NST and NST increased mighty significantly. Whether out of or under cold exposure, the Ps-NST and NST both increased mighty significantly. The NST was higher than P3-NST in control, but not significant., The NST was significantly higher than P3-NST in cold exposure. These indicated that the thermogenic capacity of tree shrews could increase significantly after cold exposure. Tree shrews could adopt the strategy that increased thermogenic capacity to adapt the cold stress. There were Ps-AR in the BAT of tree shrews and the p3-AR was not the only AR in BAT. Perhaps, NE enhanced thermogenesis by P-AR approach. UCPs which lay in the mitochondrial inner membrane of EAT^ liver and skeletal6muscle brought on the most NST, and the BAT gave the most contributions among the all. The proton leak was very important to BMR. The AR approach played an important role in the adaptive thermogenesis of tree shrews.2. The state III and IV of nutochondrial respiration of liver in tree shrews were enhanced significantly in cold. Different with persistent cold exposure compared with control, the RCR and P/O increased significantly in acute cold exposure. The respiration of state IV also increased significantly in acute cold exposure. These facts suggested that the liver indeed played an important role in the adaptive thermogenesis of tree shrews. There were obvious proton leak in live mitochondrial in cold exposure and the proton leak nearly connected with UCP2. As for the reason of the RCR and P/O increased significantly in acute cold exposure, whether drastic physiologic changes induced big changes in mitochondrial level, so the experiment results became instability even opposition to that in persistent cold exposure, or oxidative phosphorylation came into being a plenty of ATP witch needed by the physiologic change and induced the increasing of RCR. Now all of these were not clear and needed more experiments to testify.3. During cold exposure, the body weight of tree shrews increased significantly and the mass of liver and BAT decreased firstly and increased subsequently. The total RNA contents of liver and BAT increased gradually. The time that the total RNA of liver began increasing was earlier than that of BAT, but the increasing range of total RNA content of BAT was bigger than that of liver. In persistent cold exposure. The total RNA contents of liver and BAT were at high levels, but fell slowly. All these results indicated that the cells of liver and BAT could add and the expression activity of UCPs would enhance significantly in cold exposure. It suggested that the liver of tree shrews responded more rapidly to cold e...