17 



ISOTOPE TECHNIQUE IN 

 THE STUDY OF INTER- 

 MEDIARY METAROLISM 



D. RITTENBERG, assistant professor in biochemistry, college 



OF physicians and surgeons, COLUMBIA UNIVERSITY; THE LILLY 



AWARD IN BIOCHEMISTRY 



DAVID SHEMIN, associate in biochemistry, college of physicians 



AND SURGEONS, COLUMBIA UNIVERSITY 



THE STUDY of intermediary metabolism encompasses the 

 reactions undergone by cellular and dietary constituents as 

 well as the reactions involved in the formation of transient intermedi- 

 ates which occur during the degradation of various compounds to prod- 

 ucts of excretion. In studying these reactions, dietary components 

 were labeled in an attempt to trace their fate after ingestion by the 

 animal. These eflforts were but partially successful, since in all cases 

 the labels employed so changed the properties of the substance that 

 the cell treated it differently from its natural analogue. Indeed, in 

 most cases the success attained was actually due to the difference 

 between the metabolism of the foreign substance and that of its natu- 

 ral analogue. When fatty acids are administered to a normal dog 

 the only excretory products produced are carbon dioxide and water; 

 when the co-phenyl substituted fatty acids are fed (18) there are 

 excreted co-phenyl substituted acids having a carbon chain with 

 fewer carbon atoms than the original by one or more pairs. From 



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