280 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



Acenaphthene was shown by Chang and Young 203 to be absorbed by 

 adult white rats when fed at a 1% level in the diet. Thus, it was ob- 

 served that the material was excreted in the urine either as naphthalene- 

 1 ,8-dicarboxylic acid or, possibly, as naphthalic acid. It is also possible 

 that the end-product may have been excreted as a conjugated compound 

 which was decomposed by acid to yield naphthalic acid or naphthalic 

 anhydride. The formation of the naphthalic acid involves the rupture 

 of the 5-carbon ring. Since the acenaphthene structure forms an integral 

 part of the cholanthrene molecule, the question arises as to whether or not 

 the 5-membered ring in cholanthrene or in methylcholanthrene undergoes 

 fission in the body. The possible intermediary changes are given below: 



Naphthalene-1,8- Naphthalene-1,8- 



dicarboxylic acid dicarboxylic acid 



anhydride 



Possible Metabolism of Acenaphlhene in the Rat 203 



In a later study, Chang 204 investigated the digestibility of a number of 

 carcinogenic and noncarcinogenic polycyclic hydrocarbons, both when the 



Table 6 



Digestibility Coefficients of Carcinogenic and Non-carcinogenic Hydrocarbons 



in Rats" 



Coefficient of digestibility * 



Test substance Test substance 



Test substance in diet by stomach tubs 



Naphthalene 100 100 



Acenaphthene 94 90(87,94) 



Anthracene 27(10,18,47) 31(26,36) 



Phenanthrene 95(94,96) 94(93,94) 



Chrysene 24(15,19,28,36) 16(13,18) 



1,2,5,6-Dibenzanthracene 12(9,10,11,19) 4(0,7) 



3,4-Benzpyrene 58(56,56,62) 44(42,45) 



Methylcholanthrene 33(28,30,42) 32(31,32) 



a Adapted from L. H. Chang, J. Biol. Chem., 151, 93-99 (1943). 

 b Figures in parentheses are individual determinations. 



203 L. H. Chang and T,. Young, J. Biol Chem., 151, 87-91 (1913). 

 201 I,. H. Chang, J. Biol. Chem., 151, 93-99 (1943). 



