14 SUBCELLULAR PARTICLES 



both enzyme activities are visualized, with the level of ATPase apparently higher 

 than 5'-nucleotidase. 



We have evidence to suggest that high ATPase activity may be present in the 

 cell membranes of many tissues, particularly where membrane activity is high, 

 as in capillaries (fig. 13) and in the cell membranes of kidney tubule cells 

 (fig. 13). This is a section of rat kidney, from the work of Spater et al. (51), to 

 demonstrate high ATPase activity in the membranes at the base of the proximal 

 tubule cells. It is of particular interest that electron microscopy shows these mem- 

 branes to be in intimate contact with the mitochondria, the sites of ATP 

 generation. 



The original lead procedure was that of Goinori(i6) for acid phosphatase. 

 It can be used to good advantage with frozen sections of tissue fixed in cold 

 formol-calcium. Figure 14 is a section of kidney from a male rat. The proximal 

 tubule cytoplasm contains a great many 'droplets' with high acid phosphatase 

 activity. Dr. de Duve, in his chapter (8), discusses the possible relation to the 

 'lysosomes' of acid phosphatase-rich 'droplets' isolated from kidney by Straus 



(5^, 53)- 



Figure 15 is a similar section of rat liver, demonstrating peribiliary bodies 

 with high acid phosphatase activity. We are currently attempting to ascertain 

 by electron microscopy whether these bodies are identical with the 'dense bodies' 

 seen in figure 7 and discussed by de Duve (8) in relation to 'lysosomes.' We hope 

 in this fashion also to clarify their relation to the CJolgi apparatus (figs. 9, 20 

 and refs. 30, 31). 



KupfTer cells, in keeping with their phagocytic character, show high acid 

 phosphatase activity. This is undemonstrable by biochemical assay of tissue 

 homogenates yet is readily seen in stained sections of tissue in situ (fig. 15). The 

 value of such staining methods in supplementing biochemical analyses is further 

 emphasized by figure 16, a liver section from a rat fed the carcinogen, 3'-methyl, 

 4-dimethylaminoazobenzene, for 3 weeks. Its most striking aspect is the marked 

 increase in number of KupEfer cells with very high acid phosphatase activity. 

 After only 2 days on the dye, there is a decided increase in the number of 

 Kupf?er cells with high acid phosphatase activity. Such shifts in cell population, 

 enzymically heterogeneous, need to be taken into account in assessing chemical 

 data from homogenates and isolated subcellular fractions of physiologically or 

 pathologically altered tissue. Daoust (7) has plotted the changing numbers of cell 

 types in rat liver following feeding of the carcinogen, 4-dimethylaminoazobenzene, 

 and Abercrombie and Harkness (i) have done so following partial hepatectomy. 



The last staining method to be considered briefly is the tetrazolium method for 

 oxidative enzymes, now quite useful for intracellular localization (30). The 

 points at which we believe the tetrazolium links with the electron transport 

 chain of mitochondria and microsomes are shown in figure 17; this is based mostly 



