^*Corresponding author. Tel: +86-512-65880073; Fax: +86-512-65880069; E-mail: zhangzengli@suda.edu.cn

雌激素改善了维生素D受体基因敲除雌性小鼠的骨钙代谢

李冰燕，童 建，张增利

苏州大学放射医学与公共卫生学院，苏州 215123

摘 要：以维生素D受体基因敲除小鼠为模型，研究雌激素对骨钙代谢的调节是否需要维生素D受体的介导。外源性给予雌二醇一个月后，观察小鼠血钙水平的变化，同时测定小鼠骨密度，并利用胫骨非脱钙von Kossa染色观察钙化的骨小梁和未钙化的类骨质面积的变化。结果发现，外源性给予雌二醇一个月后，维生素D受体基因敲除小鼠的血钙水平增高，从(2.1±0.37) mmol/上升到(2.8±0.41) mmol/L (P<0.05)；骨密度显著改善，从(0.037±0.006) g/cm²上升到(0.048±0.007) g/cm² (P<0.05)；钙化骨小梁面积显著增加，未钙化的类骨质面积显著缩小。结果提示，外源性雌二醇对骨代谢具有非依赖于维生素D的正向调节作用。

关键词：维生素D受体；雌激素；钙平衡；骨骼矿化

中图分类号：R335.5

Exogenous estrogen improved calcium homeostasis and skeletal mineralization in vitamin D receptor gene knockout female mice

LI Bing-Yan, TONG Jian, ZHANG Zeng-Li

Radiation Medical and Public School of Soochow University. Suzhou,215123, China

Abstract: It is well known that estrogen can inhibit bone absorption, decrease bone turnover and preserve bone mass. Some studies indicated that the effect of estrogen on calcium and bone is relative to vitamin D system, while it was also reported that this effect of estrogen is independent of vitamin D. The genomic effect of 1α,25(OH)₂D₃ is mediated by the nuclear vitamin D receptor (VDR) in a ligand-dependent manner. Hypocalcemia, hyperparathyroidism and osteomalacia are developed in VDR gene knockout mice. To determine whether effect of estrogen on calcium and bone is dependent on VDR, this study examined the effect of exogenous estrogen on calcium and bone homeostasis in VDR gene knockout mice. Male and female VDR heterozygous mice were mated each other and the genotyping of their offsprings were determined by PCR. At age of 21-day, wild-type and knockout mice were weaned and treated by one of three different regimens: (1) WT-vehicle group: the wild-type mice were injected with normal saline; (2) VDRKO-vehicle group: the VDR gene knockout mice were injected with normal saline or (3) VDRKO-E group: the VDR gene knockout mice were injected with E₂, 0.2 μg per mouse subcutaneously once daily for 1 month. The bone mineral density (BMD) of mice was measured using dual-energy X-ray absorptiometry. All mice were sacrificed at age of 50-day. Blood was taken by heart puncture under anesthesia and serum calcium was measured by autoanalyser. Tibiae were removed, fixed and embedded with the methylmethacrylate (MMA), and undecalcified sections were cut．These sections were stained for mineral with the von Kossa staining procedure and counterstained with toluidine blue. Static histomorphometric analyses were performed on those stained sections. The results showed that the serum calcium level was (2.1±0.37) mmol/L in the VDRKO-vehicle mice and rose to (2.8±0.41) mmol/L in the VDRKO-E mice although it was still lower than WT-vehicle mice [(3.1±0.48) mmol/L]. BMD and mineralized trabeculer volume were increased significantly in VDR KO-E group compared with that in VDR KO-vehicle group. These results suggest that exogenous estrogen can improve calcium absorption and skeletal mineralization in a VDR-independent manner.

Key word: vitamin D receptor; estrogen; calcium homeostasis; skeleton mineralization