138 ALEXANDER L. DOUNCE 



Laskowski et al.^^ and Lang et al.^^ the enzyme is highly concentrated in 

 cell nuclei (thymus and kidney) while according to Webb'^\ Schneider and 

 Hogeboom," and Mirsky et al.^^ it is essentially mitochondrial. Clearly in 

 this case also, more work with nuclei isolated by different methods will be 

 required to settle the matter. 



Alkaline phosphatase is an enzyme the intracellular distribution of which 

 has been studied extensively by cyto- and histochemical techniques. It was 

 originally taken for granted that this enzyme was present in high concen- 

 tration in cell nuclei, largely as the result of histochemical studies (see 

 footnote 80), but also because isolated chromosomes^" and isolated nuclei 

 generally showed high enzyme activity. Subsequently, it was demonstrated 

 that diffusion of the newly formed calcium phosphate, before its precipita- 

 tion, could cause artifacts in the histochemical method,''^ ■^** and doubts 

 arose as to whether the apparent nuclear localization of the enzyme was 

 valid. These doubts were strengthened by the observation that a different 

 histochemical procedure showed a lack of alkaline phosphatase in liver cell 

 nuclei. ^^* 



Nuclei isolated in dilute citric acid from calf liver cells show a high alka- 

 line phosphatase activity relative to that of the whole homogenate, but we 

 now realize that this could be the result of the adsorption of finely divided 

 mitochondrial fragments, as in the case of cytochrome oxidase. However, 

 nuclei isolated by the new technique using calcium chloride and sucrose 

 also seem to have alkaline phosphatase in specific activity as high as that 

 of the homogenate.'*^ Mirsky et alP found rather low concentrations of 

 alkaline phosphatase in their Behrens-type nuclei, except in horse liver. 

 Thus the presence or absence of alkaline phosphatase in cell nuclei is a 

 matter requiring further study, but at the present time it can be stated 

 that the concentration of this enzyme, in certain cell nuclei at least, is 

 certainly lower than was indicated by the early work. 



Acid phosphatase is probably not generally present in cell nuclei in high 

 concentration, and, judging from the work of Pallade,'*^ who showed it to 

 be predominantly a mitochondrial enzyme in rat liver cells, it may actually 

 be absent from some types of cell nuclei. 



Certain peptidases and proteases have been reported as present in cell 

 nuclei isolated in aqueous media, by Miller, Bounce, and assistants^ and 

 by Lang et al.^^ On the other hand, Maver et a/.'** found very low catheptic 



"» R. F. Witter, M. A. Cottone, and A. L. Bounce, unpublished. 

 "1 M. Webb, Nature 169, 417 (1952). 



132 B. F. Martin and F. Jacoby, J. Anat. 83, 351 (1949). 



133 A. B. Novikoff, Science 113, 320 (1951). 

 "* A. Emery and A. L. Bounce, unpublished. 

 1" G. E. Palade, Arch. Biochem. 30, 144 (1951). 



"« M. E. Maver, A. E. Greco, E. L0vtrup, and A. J. Balton, J. Natl. Cancer Inst. 

 13, 687 (1952). 



