A study on the mechanism of bone lesion by cadmium Effect of cadmium on the bone formation in cultured MC3T3-E1

为进一步了解镉致骨损伤的机制，从DNA合成、碱性磷酸酶活力和胶原合成等方面探讨镉对骨细胞分化的影响。细胞培养3d后，在含10%胎牛血清的培养液中加入金属离子，在37ﾟC、5%CO2的空气中培养7d。10^~(-8)M镉对细胞ALP活性无明显影响，但10^~(-7)M和10^~(-6)M镉使细胞ALP活性分别下降25%和30%。10~(-5)-M-Cd可显著降低ALP活性。10^~(-5)~(-5)~(-5)~(-5)Cd暴露后，DNA含量和羟脯氨酸含量也下降，10~(-6)~(-6)M Cd对上述两项指标无明显影响。鉴于锌对Cd的毒性有一定的保护作用，我们还研究了锌与Cd共存对MC3T3-E1的影响。有趣的是，Cd浓度为10^lt；-5&gt；M时，锌浓度为10^lt；-4&gt；M时，形态变化有所改善。加入10^~(-4)~(-4)~(-4)~(-4)~(-5)~(-5)~(-5)~(-5)~(-5)~(-5)~(-5)~(-5)~(-1)~(-1)~(-1)~(-1)~(-5)~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)~(-1)-M~(-1)锌，可使镉引起的碱性磷酸酶(ALP)活性、蛋白质含量和羟脯氨酸含量恢复正常。本研究提示，低浓度镉长期暴露使碱性磷酸酶失活，可能会影响成骨细胞的功能。

To obtain further information on the mechanism of bone damage caused by cadmium(Cd), the effect of Cd on the differentiation of bone cells (MC3T3-E1) were examined by quantitating DNA synthesis, alkaline phosphatase(ALP) activity and collagen synthesis.After cells were cultured for 3 days, metal ions were added to the medium containing 10% fetal bovine serum and cells were subsequently cultured for 7 days at 37ﾟC in 5% CO_2 in air. Although 10^<-8>M of Cd have no significant influence on ALP activity of the cells, 10^<-7>M and 10^<-6>M of Cd decreased ALP activity by 25% and 30% of control value. 10^<-5>M Cd remarkably decreased ALP activity. DNA content and hydroxyproline content were also decreased by exposure to 10^<-5>M of Cd, less than 10^<-6>M Cd didn't affect both the parameters.Since there are some reports that zine(Zn) has a protective effect against the toxicity of Cd, we also examined the effect of Zn coexisting with Cd on MC3T3-E1. Interestingly, morphological changes by 10^<-5>M of Cd were improved by 10^<-4>M of Zn. ALP activity, protein content, and hydroxyproline content decreased by exposure to 10^<-5>M of Cd were also recovered by the addition of 10^<-4>M Zn to the culture medium.The present study suggests that ALP molecule, sythesized in osteoblastic cells and bound to cell membrane, may be the primary target of Cd. The inactivated ALP by exposure to low concentration of Cd for a long period may affect the function of osteoblastic cells in bone.