Studies with Deuterium Steroids 35 



localization of the isotope proves that the union of catalyst 

 and the organic molecule is a highly specific one dictated by 

 the various features of the molecule. More important than this 

 for biochemical purposes, the studies show that isotope in a 

 chemically labile position may still contribute very significant 

 information, since Bloch, using cholesterol from the exchange 

 reaction, was able to demonstrate the conversion of cholesterol 

 to pregnanediol (Bloch, 1945). Since almost surely this 

 transformation was accomplished through an intermediate 

 such as progesterone or a similar a/S-unsaturated ketone, the 

 chemically labile deuterium of the ring system was not lost 

 and was in fact retained to a very considerable extent. Recal- 

 culation of the data of Bloch, using the isotope distribution 

 we have found, indicates that 80 per cent of the urinary 

 pregnanediol was derived from the serum cholesterol. 



The isotopically-labelled steroid hormones permit study 

 of the following points which could not be discovered by 

 alternative methods: (1) It is possible to distinguish clearly 

 between the endogenous glandular production and the 

 administered hormone; (2) It is possible to detect transforma- 

 tions that take place in such limited amount as to be undetect- 

 able by ordinary means; (3) It is possible to set precise 

 quantitative limits on the extent to which a particular trans- 

 formation takes place or conversely to demonstrate the 

 absence of such a transformation. These can be well illus- 

 trated from a specific experiment. 



A normal man received 100 mg. of labelled testosterone 

 intramuscularly in a single injection in solution in sesame oil 

 containing a small amount of benzyl alcohol. Urine was 

 collected for twenty-four hours after the injection. The 

 urinary steroids were isolated by the procedure developed and 

 standardized by Dobriner (Dobriner, Lieberman and Rhoads, 

 1948; Lieberman, Dobriner, Hill, Fieser and Rhoads, 1948). 

 The a-ketonic fraction was chromatographed and the various 

 fractions from the chromatogram were examined for the 

 presence of deuterium by infra-red spectrometry (Dobriner, 

 Kritchevsky, Fukushima, Lieberman, Gallagher, Hardy, 



