Skinner D C, Moodley G, Buffenstein R
Physiology Department, Medical School, University of the Witwatersrand, Johannesburg, Republic of South Africa.
Gen Comp Endocrinol. 1991 Mar;81(3):500-5. doi: 10.1016/0016-6480(91)90178-9.
The Damara mole-rat (Cryptomys damarensis) leads a strictly subterranean existence in an extensive maze of plugged burrows and eats a strictly herbivorous diet. An obvious source of vitamin D3 (D3), an important hormone in mineral homeostasis, therefore is lacking in this mammal. The effects of orally ingested D3 on mineral balance were investigated. In the normal D' status group of mole-rats, the apparent fractional intestinal absorption of calcium (91.1%), magnesium (91.2%), and inorganic phosphorous (91.2%) was high and increased slightly, (calcium, 94.5%; magnesium, 93.2%; inorganic phosphorous, 92.9%) after D3 administration. The amount of element absorbed was positively correlated with the amount ingested (P less than 0.001), suggesting that absorption occurs via a nonsaturable process. This might be an adaptation to the sparseness of natural food. The observed positive retention of calcium (94%), magnesium (85%), and inorganic phosphorous (99.9%) is attributed to their evergrowing teeth. These teeth are constantly worn down during digging and it is speculated that they represent a mineral "sink," assisting in the maintenance of mineral homeostasis. It is also hypothesized that mole-rats have adapted to an environment devoid of D3 and can attain sufficient calcium for their needs via nonvitamin D3-dependent processes. Although mole-rats have the "machinery" to use D3 and D3 can affect mineral balance, this effect may be disadvantageous if invoked.
达马拉鼹形田鼠（Cryptomys damarensis）在由堵塞的洞穴构成的广阔迷宫中过着严格的地下生活，并且以严格的草食性饮食为生。因此，这种哺乳动物缺乏维生素D3（D3）这一矿物质稳态中的重要激素的明显来源。研究了口服D3对矿物质平衡的影响。在正常D状态的鼹形田鼠组中，钙（91.1%）、镁（91.2%）和无机磷（91.2%）的表观小肠吸收分数很高，在给予D3后略有增加（钙为94.5%；镁为93.2%；无机磷为92.9%）。吸收的元素量与摄入的量呈正相关（P小于0.001），这表明吸收是通过非饱和过程发生的。这可能是对天然食物稀缺的一种适应。观察到的钙（94%）、镁（85%）和无机磷（99.9%）的正保留归因于它们不断生长的牙齿。这些牙齿在挖掘过程中不断磨损，据推测它们代表一个矿物质“库”，有助于维持矿物质稳态。还假设鼹形田鼠已经适应了缺乏D3的环境，并且可以通过非维生素D3依赖的过程获得足够满足其需求的钙。尽管鼹形田鼠具备利用D3的“机制”，并且D3可以影响矿物质平衡，但如果引发这种影响可能是不利的。
