25 



The Possible Role of Chelation 



in Decalcification of Biological Systems 



G. NEIL JENKINS, Dej)artinent of Physiology, Medical School, King's 

 College, Newcastle upon Tyne, England 



C. DAWES, Department of Chemistry, Harvard School of Dental Medi- 

 cine. Boston, jMassachusetts 



NEUMAN and Neuman ( 1958 ) have pointed out in their stimulating 

 monograph the three most reasonable hypotheses to solve the prob- 

 lem of how the calcified tissues may dissolve in the surrounding 

 fluids which are in general believed to be already supersaturated 

 with respect to bone mineral. The most discussed possibility is that 

 the environment of the bone cells is maintained at a lower pH and 

 is therefore locally unsaturated as a result of metabolic acids' leaving 

 the cells. A second possibility is that either the cells or the bone 

 matrix releases a chelating substance which can dissolve the bone 

 salts even in an environment which, on an ionic basis, is saturated 

 or supersaturated. Thirdly, if the cell were surrounded by a high 

 concentration of certain ions which take part in surface exchange 

 (e.g. magnesium, carl^onate, or citrate), these ions could increase 

 the apparent solubility of the bone. 



The Nature of Chelation and the Chelating Agents 

 Present in Tissues 



In addition to forming the familiar salts with metallic ions, certain 

 acids are capable of forming complex ions such as ferricyanides or 



637 



