Mechanism and function of high vitamin D receptor levels in genetic hypercalciuric stone-forming rats
Mechanism and function of high vitamin D receptor levels in genetic hypercalciuric stone-forming rats
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DOI：
10.1359/jbmr.041120
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发表时间：
2005-03-01
影响因子：
6.2
通讯作者：
Favus, MJ
中科院分区：
文献类型：
--
作者：
Karnauskas, AJ;van Leeuwen, JPTM;Favus, MJ
探讨了GHS大鼠VDR增加的功能状态及机制。GHS大鼠基础VDR和calbinding增加。1,25(OH)(2)D-3增加了对照大鼠的VDR和钙结合，但对GHS大鼠没有影响。GHS大鼠VDR半衰期延长。本研究支持了GHS大鼠VDR升高的机制和功能状态。遗传性高钙尿酸结石形成（GHS）大鼠由于肠道钙吸收和骨吸收增加，肾脏钙吸收减少而引起的高钙尿形成钙性肾结石。正常血清1,25-二羟基维生素D-3 [1,25(OH)(2)D3]水平和维生素D受体（VDR）蛋白升高提示维生素D应答基因的高表达率可能介导高钙尿症。VDR升高的机制和受体功能状态尚不清楚。材料与方法：GHS和非结石形成对照（NC）雄性大鼠（平均249 g），饲喂正常钙饲料，在注射环己亚胺（6 mg/100 g， IP）前24 h，腹腔注射1,25(OH)(2)D-3 （30 ng/100 g BW）或载药，0-8 h后处死。ELISA和Western blot检测十二指肠VDR， Western blot检测十二指肠和肾脏钙结合蛋白（9和28 kDa）。结果与结论：经Western blot检测，GHS大鼠十二指肠VDR蛋白比NC大鼠增加了2倍（633 +/- 62比388 +/- 48 fmol/mg蛋白，n = 4, p < 0.02）， 1,25(OH)(2)D-3进一步增加了NC大鼠的VDR和钙结合蛋白（9和28 kDa），而GHS大鼠则没有。GHS大鼠十二指肠VDR半衰期延长（2.59 +/- 0.2 h比1.81 +/- 0.2 h, p < 0.001）。1,25(OH)(2)D-3使NC大鼠十二指肠VDR半衰期较未处理的GHS大鼠延长（2.59 +/- 0.2 h对2.83 +/- 0.3 h，无统计学意义）。本研究支持以下假设：VDR半衰期的延长增加了VDR组织水平，并通过维生素d调节的钙在肠道、骨骼和肾脏中的转运，介导VDR调节基因的增加，从而导致高钙尿。
The functional status and mechanism of increased VDR in GHS rats were investigated. Basal VDR and calbindins were increased in GHS rats. 1,25(OH)(2)D-3 increased VDR and calbindins in controls but not GHS rats. VDR half-life was prolonged in GHS rats. This study supports the mechanism and functional status of elevated VDR in GHS rats.Introduction: Genetic hypercalciuric stone-forming (GHS) rats form calcium kidney stones from hypercalciuria arising from increased intestinal calcium absorption and bone resorption and decreased renal calcium reabsorption. Normal serum 1,25-dihydroxyvitamin D-3 [1,25(OH)(2)D3] levels and increased vitamin D receptor (VDR) protein suggest that high rates of expression of vitamin D-responsive genes may mediate the hypercalciuria. The mechanism of elevated VDR and state of receptor function are not known.Materials and Methods: GHS and non-stone-forming control (NC) male rats (mean, 249 g), fed a normal calcium diet, were injected intraperitoneally with 1,25(OH)(2)D-3 (30 ng/100 g BW) or vehicle 24 h before cycloheximide (6 mg/100 g, IP) and were killed 0-8 h afterward. Duodenal VDR was measured by ELISA and Western blot, and duodenal and kidney calbindins (9 and 28 kDa) were measured by Western blots.Results and Conclusions: Duodenal VDR protein by Western blot was increased 2-fold in GHS versus NC rats (633 +/- 62 versus 388 +/- 48 fmol/mg protein, n = 4, p < 0.02), and 1,25(OH)(2)D-3 increased VDR and calbindins (9 and 28 kDa) further in NC but not GHS rats. Duodenal VDR half-life was prolonged in GHS rats (2.59 +/- 0.2 versus 1.81 +/- 0.2 h, p < 0.001). 1,25(OH)(2)D-3 prolonged duodenal VDR half-life in NC rats to that of untreated GHS rats (2.59 +/- 0.2 versus 2.83 +/- 0.3 h, not significant). This study supports the hypothesis that prolongation of VDR half-life increases VDR tissue levels and mediates increased VDR-regulated genes that result in hypercalciuria through actions on vitamin D-regulated calcium transport in intestine, bone, and kidney.