RELEASE OF ALCOHOLS FROM ESTERS 41 



When mammalian kidney sections are studied by this method, 

 the azo dye is precipitated in the brush borders and also in the 

 nuclei of white cells (Table III) . It is usually not found in the 

 nuclei of the other cells present in the tissue. There are prob- 

 ably two reasons why the low concentration of phosphatase in 

 the other cell nuclei cannot be demonstrated by this technique. 

 In the first place, the azo dye is not completely insoluble in 

 water and it is probable that, unless the rate of production of 

 the azo compound at a particular site exceeds a given limit, 

 precipitation does not occur in the section. Secondly, the dia- 

 zonium hydroxide also reacts with certain components of the 

 tissue section themselves, producing a background stain. Very 

 small amounts of precipitated azo dye cannot be distinguished 

 from the background staining. It may also, of course, be pos- 

 sible that nuclear enzymes react less vigorously with /3-napthol 

 phosphate than with glycerophosphate. Provided that the azo 

 dye resulting from the interaction of the phenol and diazonium 

 hydroxide is sufficiently insoluble, the same result is obtained 

 with any mixture of phenol phosphate and diazonium hydrox- 

 ide. Table III summarises results which have been obtained 

 with a number of different bases. 



TABLE III 



Summary of results obtained by exposing kidney sections containing active 

 phosphatase to a solution at pK 9.3 containing a phenol phosphate and a 

 diazotised amine. The remarks refer to the localization of dye produced by 

 the interaction of the diazonium hydroxide with a phenol liberated by the 

 action of the enzyme on a phenol phosphate. 



Site of Dye Precipitated with 



not 



