McCary L C, Smith C M, DeLuca H F
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, USA.
J Bone Miner Res. 1997 Nov;12(11):1944-51. doi: 10.1359/jbmr.1997.12.11.1944.
Our previous work has shown that op/op mice hyperabsorb dietary calcium in the vitamin D-deficient state and shunt that calcium into bone. Under these conditions, the op/op mice are hypocalcemic. The purpose of this study was to examine calcium metabolism and bone mineralization in vitamin D-deficient op/op mice. First, the op/op mice and their normal littermates were placed on a vitamin D-deficient, low phosphorus diet to limit bone mineralization. Under these circumstances, op/op mice survived, even when calcium was also removed from the diet. If the diet contained phosphate, op/op mice died from hypocalcemic tetany when calcium was also removed from the diet. Furthermore, serum calcium levels became similar to wild type in the op/op mice administered the vitamin D-deficient, low phosphorus diet, and op/op mice were able to increase serum calcium in response to 1,25-dihydroxyvitamin D3. The op/op mice developed rickets when their serum phosphorus level was too low to support bone mineralization. The op/op mice became hypophosphatemic on regimens in which normal mice were able to maintain normal serum phosphorus levels. It appears that the op/op mouse simply requires a higher dietary calcium and phosphorus level to prevent rickets and hypocalcemic tetany since the bone is not available as a source of these minerals. However, the ability of the op/op mouse to mineralize bone at low serum calcium and phosphorus levels remains unexplained.
我们之前的研究表明，op/op小鼠在维生素D缺乏状态下会过度吸收膳食钙，并将这些钙分流至骨骼中。在这些条件下，op/op小鼠会出现低钙血症。本研究的目的是检测维生素D缺乏的op/op小鼠的钙代谢和骨矿化情况。首先，将op/op小鼠及其正常同窝小鼠置于维生素D缺乏、低磷饮食中，以限制骨矿化。在这种情况下，即使从饮食中去除钙，op/op小鼠仍能存活。如果饮食中含有磷酸盐，当从饮食中去除钙时，op/op小鼠会死于低钙性手足搐搦。此外，给予维生素D缺乏、低磷饮食的op/op小鼠血清钙水平变得与野生型相似，并且op/op小鼠能够对1,25-二羟维生素D3作出反应而升高血清钙。当op/op小鼠的血清磷水平过低而无法支持骨矿化时，它们会发生佝偻病。在正常小鼠能够维持正常血清磷水平的饮食方案下，op/op小鼠会出现低磷血症。似乎op/op小鼠仅仅需要更高的膳食钙和磷水平来预防佝偻病和低钙性手足搐搦，因为骨骼无法作为这些矿物质的来源。然而，op/op小鼠在低血清钙和磷水平下矿化骨骼的能力仍无法解释。
