Study On The Relationship Between Age And The Contents Of Heavy Metal Elements Such As Cadmium,Chromium,Cobalt,Lead,Manganese And Thallium In Human Bone And Blood

Objective:To explore the relationship between age and the contents of heavy metal elements such as cadmium,chromium,cobalt,lead,manganese and thallium in human bone and blood;To explore the relationship between osteopenia and the contents of above six metal elements in human bone and blood.Methods:The cancellous bone of the greater trochanter was taken during total hip arthroplasty as bone samples of the aged,and the cancellous bone of tibia was obtained during anterior cruciate ligament reconstruction surgery as bone samples of young people.All of the bone samples were weighed(wet weight)and recorded.For every patient,2～3ml of venous blood was sampled three days after surgery,and the bone mineral density(BMD)was measured by dual energy X-ray absorptiometry(DEXA)to distinguish normal group and osteopenia group.Bone samples were dried in a lyophilizer at-40℃ to-50℃ for 2 days till the weight is constant,then samples were reweighed(dry weight)and the weight loss rate was calculated.For preparation of test liquid,first the bone samples were placed in a 25ml sharp-bottomed flask,then 2ml of concentrated nitric acid was added to soak bones overnight.After that,6ml 30%hydrogen peroxide(30%H2O2)was added and the mixture was digested at 90～100℃for 24 hours with magnetic heated stirrer.Limpid and translucent digestion solution was diluted with ultrapure water to 20ml and reserved at 4℃.As for each blood sample,lml blood sample was transferred to 50ml sharp-bottomed flask and then 1ml concentrated nitric acid was added into it overnight.The next day,10ml 30%hydrogen peroxide was added and the mixture was digested at 90～100℃ for 24 hours with magnetic heated stirrer.Till the solution become transparent,we used ultrapure water to dilute it to 20ml and reserved at 4℃.The bone diluent and blood diluent were all measured by inductively coupled plasma mass spectrometry(ICP-MS)to detect element concentration,and then corresponding bone content(ng/g)and blood content(ng/ml)were calculated.According to patients’ age,the total samples were divided into young group(n=7)and old group(n=16).Then the old group was subdivided into normal group(n=9,-1<T<1)and osteopenia group(n=7,T<-1.5)according to patients’BMD.We compared the bone and blood contents of six elements(cadmium,chromium,cobalt,lead,manganese,and thallium)between normal group and young group or osteopenia group to evaluate the distribution characteristics of above six heavy metal elements in bone and blood with age.Results:With the increase of age,the content of chromium,cobalt,and thallium in human bones decreased,while the content of cadmium showed a significant increase,and the changes in bone content of these elements were not accompanied by changes in blood content.Besides,there was no obvious relationship between age and bone content of manganese and lead.Notably,cobalt has been shown to be closely related to osteopenia.Conclusion:Accompanied by senescence of human body,cobalt,chromium,and thallium translocate from the bone to the extra-bone,which may aggravate the risk of other tissues and organs in the elderly.However,the bone content of cadmium increases with age.These changes with age in the bone content of heavy metal elements is likely to be related to the equilibrium of bone metabolism in senescent people.For blood content of these elements,no significant difference was observed between young and old people.Besides,only cobalt was proved to be significantly relevant to osteopenia.