DIFFUSION OF CALCIUM PHOSPHATE 



37 



high affinity for calcium phosphate. In these two types of sec- 

 tion, the distribution of phosphatase as demonstrated by the 

 glycerophosphate technique with sections containing active 

 enzyme is such that the brush-border regions of the kidney con- 

 tain the highest concentrations of phosphatase, newly formed 

 collagen the next highest, and nuclei a moderate to low concen- 

 tration of phosphatase. It is thus clear that some sites which 

 appear to contain phosphatase have a high affinity for calcium 

 phosphate but that there is no correlation between this affinity 

 and the absolute concentrations of phosphatase appearing in 

 the cells. 



The Ability of Calcium Phosphate to Diffuse within a 

 Section 



As noted just above, when a tissue section is heated it loses 

 its phosphatase activity, but retains its affinity for calcium phos- 



Inactive 

 section 



Active 

 section 



^^ 



^mmzzmmz 



Glass slide 

 Fig. 2. Illustrating arrangement of active and inactive sections on a slide 



required to test for diffusion artefacts. 



phate. It is therefore possible by superimposing a section con- 

 taining active enzyme upon a section in which the enzyme has 

 been destroyed to test the extent to which calcium phosphate 

 may diffuse in sections from one site to another. It is best to 

 arrange the sections as illustrated in Fig. 2 with the inert sec- 

 tion lying underneath the section containing active enzyme, so 

 as to observe the maximum effect of diffusion of calcium phos- 

 phate. In the first studies which were made using this tech- 



