Metabolism of ^*C-Labelled Steroids 11 



urinary elimination of progesterone than did Riegel and 

 co-workers could probably be explained by the difference in 

 injection routes, since these authors used intraperitoneal 

 administration. The absorption through the liver which 

 occurred in this case would lead to a greater breakdown to 

 CO2 and a greater excretion into the faeces through the bile. 

 It is indeed well known that progesterone and its derivatives 

 are detoxified in the liver (Leblond, 1942). 



The radioactivity figures for organs were not very informa- 

 tive. They may be expected to become most useful when two 

 further steps in the progress of this investigation are taken: 

 the chemical analysis of the nature of the radioactive material 

 present, a study which will require the use of such techniques 

 as paper chromatography; and the autoradiographic localiza- 

 tion of the radioactive material. Thus, in the case of the 

 uterus, sections of which are shown in Figs. 1 and 2, the 

 radioactivity content as estimated with the Geiger counter 

 did not significantly differ from that of other organs. Never- 

 theless, some radioactive material was selectivelv concentrated 

 in the epithelial cells. 



Summary 



Preliminary experiments have been carried out with 

 oestrone, progesterone and deoxycorticosterone acetate 

 labelled with ^*C. The results obtained and some possibilities 

 for future work are discussed. 



Acknowledgemeni 



This work was carried out with the help of grants from the 

 National Cancer Institute of the U.S. Public Health Service 

 (Department of Biochemistry) and of the National Cancer 

 Institute of Canada (Department of Anatomy). 



REFERENCES 



Albert, S., Heard, R. D. H., Leblond, C. P., and Saffran, J. (Id49). 



J. biol. Chetn., 177, 247. 

 Leblond, C. P. (1942). Arner. J. med. Sci., 204, 566. 



