Studies on mechanism of heat production in the house musk shrew (Suncus murinus) with unstable body temperature.

麝香鼩（Suncus murinus）是一种独特的实验动物，被认为不耐冷。当它在低温室内保存时，它变得低温，不动，最终死亡。1)我们发现，太阳鼠比小鼠更容易受到寒冷的影响，它们对寒冷不耐受的一个原因是棕色脂肪组织（IBAT）的产热和脂质消耗功能障碍。2)轻度低温暴露和高脂肪饮食均未诱导BAT中解偶联蛋白1 （Ucp1）和ⅱ型5′-脱碘酶（D2） mrna的上调。然而，低温暴露和高脂肪饮食的组合显著增加了这两种mrna。因此，番石榴的寒性不耐可能与饮食成分有关。3)对suncus Ucp1进行cDNA克隆，并与其他物种进行比较。推导出的氨基酸序列与其他哺乳动物UCP1具有较高的同源性。Northern blot分析显示BAT中的mRNA与其他哺乳动物一样。然而，在一个重要的产热残基中观察到氨基酸残基的差异。基因组序列分析表明，这种差异存在于我们两个遗传上遥远的实验室菌落中。这些结果表明，番荔枝的耐冷性可能源于UCP1的低产热活性。

The house musk shrew (Suncus murinus), or suncus, is a unique experimental animal that is thought to be cold intolerant. When it is maintained in low temperature room, it becomes hypothermic, immobile, and eventually dies.1) We found that the suncus are more susceptible to cold than mice, and that one reason for their cold intolerance is a malfunction of heat production and lipid depletion in brown adipose tissue (IBAT).2) Neither mild cold exposure nor a high-fat diet alone induced up-regulation of the mRNAs for uncoupling protein 1 (Ucp1) and type II 5'-deiodinase (D2) in BAT. However, combinations of cold exposure and high-fat diet significantly increased both mRNAs. Therefore, cold intolerance in suncus may be partly caused by dietary components.3) We did cDNA cloning of suncus Ucp1 and compared it to other species. The deduced amino acid sequence showed high homology with other mammalian UCP1. Northern blot analysis revealed mRNA in BAT as in other mammals. However, a difference in an amino acid residue was observed in an important residue for thermogenesis. Genomic sequence analysis showed that this difference existed in our two genetically distant laboratory colonies. These results suggest that the cold intolerance in suncus may be derived from low thermogenic activity of UCP1.