低钙饲料对大鼠胫骨上下段骨骼的影响

EFFECTS OF LOW CALCIUM DIET ON DISTAL AND PROXIMAL TIBIAL METAPHYSIS IN MALE RATS

目的: 评价低钙饮食对大鼠胫骨上段(PTM)和下段(DTM)骨骼的影响,了解其变化规律。方法: 3月龄SD普通级雄性大鼠40只,随机分为五组。第1、2组饲养1个月,分为正常对照组Control(Ca 1.0%)和极低钙组VLCD(Ca 0.1%),余下三组饲养3个月,分为正常对照组Control(Ca 1.0%)、极低钙组VLCD(Ca 0.1%)和低钙组LCD(Ca 0.3%)。各组动物饲以不同钙含量的精制饲料。处死前注射双荧光标记。实验结束时,取左侧胫骨行骨形态计量学检测。结果: 低钙饮食1个月后,DTM骨量和其它各参数未出现显著变化,而PTM骨小梁面积百分率(%Tb.Ar)减少38%(P<0.05),代表吸收的参数值如单位骨小梁周长破骨细胞( N.OC/Tb.Pm)增加98%(P<0.01)。3个月后,DTM骨量显著下降,%Tb.Ar在VLCD组降低44%(P<0.001)。此时PTM骨量进一步丢失。PTM和DTM动态参数显示骨形成的参数荧光周长百分数(%L.Pm)、骨矿化沉积率(MAR)和骨形成率(BFR/BS)均呈现无统计意义的增加,N.OC/Tb.Pm亦增加至不同程度。VLCD与LCD相比,骨骼均呈现相似的变化,两组各指标差异均无显著性。但LCD组各指标变化程度均有所减弱。结论: 低钙对PTM和DTM骨骼产生不同程度的影响,骨高转换的PTM比代谢缓慢的DTM骨丢失程度严重,这种影响的差异可能与机体动用不同部位骨钙的快慢有关。

Objective:To investigate the effect of a low calcium diet on the distal and proximal tibial metaphysis in male rats using bone histomorphometrical techniques. Methods:Forty 3-month-old male Sprague-Dawley(SD) rats, with a mean weight of 280±22g, were randomized into five groups. Group one and group two were fed a normal diet (Ca 1.0%) and a very low calcium diet (VLCD ,Ca 0.1%) respectively for one month,and the rest three groups were fed a normal diet (Ca 1.0%), a very low calcium diet (VLCD, Ca 0.1%) and a low calcium diet (LCD , Ca 0.3%) respectively for three months. All animals received double bone fluorochrome labeling prior to sacrifice. At the end of experiment, the left tibiae were harvested for bone histomorphometrical evaluations. Results:After one month, compared to control group, distal tibial metaphysis(DTM) of VLCD did not change significantly but proximal tibial metaphysis(PTM) was decreased significantly whose percent trabecular area (%Tb.Ar) was decreased to 38% (P<0.05) and osteoclast number per mm (N.Oc/Tb.Pm) increased 98% (P<0.01). After three months, compared to control the bone volume of VLCD in DTM was significantly reduced to 44%(P<0.001)and PTM lost much more bone mass. Dynamic data of DTM and PTM in VLCD showed bone formation indices such as percent labeled perimeter (L.Pm%) , mineral apposition rate (MAR) and bone formation rate (BFR/BV) increased without significance and N.Oc/Tb.Pm increased to different extent . The changes of static and dynamic data in LCD were similar to and less than those in VLCD. Conclusion:Low calcium exerted its effect on DTM and PTM differently. PTM with high bone turnover lost much more bone mass than DTM with low bone turnover which were related to the speed of body moving skeletal calcium in different site.