上皮钙通道基因在维生素D受体和Calbindin-D28k双基因敲除鼠中的变化

目的研究上皮钙通道TRPV5和TRPV6基因与维生素D受体(VDR)和钙结合基因Calbindin-D28k的关系,以及肾钙的重吸收减少是否与TRPV5和TRPV6基因表达减少有关。方法制备VDR和CaBP-D28k双基因敲除小鼠,普通和高钙食物喂养下,检测野生型鼠(WT),CaBP-D28(-/-),VDR(-/-),和VDR(-/-)/CaBP-D28k(-/-)鼠的体重、摄食量及血尿参数值,用实时RT-PCR的方法检测各种鼠肾脏TRPV5和TRPV6的mRNA水平。结果普通饮食下,双基因敲除小鼠尿钙的分泌和血清甲状旁腺激素水平更高。TRPV5和TRPV6两者的表达在CaBP-D28k敲除鼠中均无变化,而在VDR敲除鼠和双基因敲除鼠中下调的幅度相当。高钙饮食下,VDR及双基因敲除小鼠的血离子钙水平正常。所有小鼠这两个基因的表达普遍降低,而在VDR和双基因敲除鼠中的表达更低。结论这些结果证实了上皮钙通道基因受钙和维生素D的调节,CaBP-D28k的缺失对两者无影响。肾钙的重吸收减少与TRPV5和TRPV6基因表达无明显关系。

Changes of Epithelial Calcium Channels Genes in Vitamin D Receptor/ Calbindin - D28k Double Knockout Mice

Objective To investigate the relationship between the epithelial calcium channels genes TRPV5,TRPV6 and the vitamin D receptor(VDR),calcium-binding gene Calbindin(CaBP)-D28k,as well as whether the decrease in renal calcium reabsorption is associated with a decrease in TRPV5 and TRPV6 expression.Methods To generate VDR/CaBP-D28k double knockout(KO)mice,body weight,diet intake and serum,urinary parameters of WT,CaBP-D28(-/-),VDR(-/-)and VDR(-/-)/CaBP-D28k(-/-)mice were determined on regular and high Ca-Lac diet.The mRNA levels of TRPV5 and TRPV6 genes in the kidneys were quantified by real time RT-PCR.Results On regular diet,urinary calcium excretion and serum parathyroid hormone(PTH)levels in the double knockout(KO)mice were higher.CaBP-D28k ablation had little effect on TRPV5 or TRPV6 expression,whereas the levels of both TRPV5 and TRPV6 were not significantly different between the VDR(-/-)and the double KO mice.On the high Ca-Lac diet,blood-ionized calcium levels were normal in the VDR and the double KO mice.The expression of these two genes was generally lower in all the mice than when they were on the regular diet.The relative expression levels in the VDR(-/-)and the double KO mice remained lower than in the WT and the CaBP-D28k(-/-)mice.Conclusion These results confirm that the epithelial calcium channels are regulated by both calcium and vitamin D,and ablation of CaBP-D28k has no stimulatory effects on both channels.The decrease in renal calcium reabsorption is not associated with a decrease in TRPV5 and TRPV6 expression.