Metabolism of i*C-Labelled Steroids 13 



En 1951 (R. Courrier, A. Horeau, M. Marois et F. Morel, 1951, C. R. 

 Acad. Sci., Paris, 232, 776) une thyroxine de tres forte radioactivite 

 sp^cifique (30 millicuries sur 12-5 mg. de thyroxine; 70 coups/minute 



par TTTT^Trp: de gamma au moment de I'experience) fut injeetee par voie 



veineuse a diverses especes animates. Les animaux traites furent 

 sacrifies deux heures apres et Ton preleva chez eux sang, plasma, ante- 

 hypophyse, post-hypophyse et differents organes. 



Les resultats peuvent se resumer ainsi: (1) La penetration de la 

 thyroxine dans I'hypophyse varie selon les especes. (2) Chez les 

 animaux oil le phenomene est decelable, e'est dans Yhypophyse 

 posterieure que la thyroxine penetre davantage. II reste a determiner la 

 signification physiologique de ce phenomene. 



II serait interessant d'etablir si la progesterone et I'acetate de desoxy- 

 corticosterone radioactifs retrouves par M. Leblond dans I'hypophyse 

 totale, se concentrent dans la posthypophyse. 



Heidelberger: In 1947 Jones and I did some work on the carcinogenic 

 hydrocarbon [9:10-^*C] dibenzanthracene, and the results of our studies 

 on excretion were very similar to those of Dr. Leblond for the steroids. 

 I wonder whether this might be a general phenomenon, based not upon 

 biological properties but largely upon the solubility of the compound. 

 It is a large water-insoluble molecule. The difference in excretion 

 pattern you observe with the deoxycorticosterone might be due 

 primarily to its greater water-solubility. 



I would also like to say that we have used paper chromatographic 

 methods for separating derivatives of carcinogenic hydrocarbons, based 

 on a modification of Zaffaroni's procedure. 



Leblond: That water-insoluble molecules are more likely to be 

 excreted in the bile, and water-soluble ones in the urine is true. Thus, 

 thyroxine is excreted in the bile and diiodotyrosine in the urine. 

 However, it is only part of the story. For instance, the water-soluble 

 iodine ion is excreted to some extent in the bile. 



