DIGESTION AND ABSORPTION OF HYDROCARBONS 281 



test substances were administered by stomach tube to rats and when 

 they were incorporated in the diet. Table G summarizes these data. 



With the exception of 1,2,5,6-dibenzanthracene, which was not ab- 

 sorbed in any appreciable amount, and of chrysene, anthracene, and 

 methylcholanthrene, which were utilized to an average extent of 20, 29, 

 and 32%, respectively, the other poly cyclic hydrocarbons tested were 

 absorbed to a large degree from the gastrointestinal tract of the rat. 



According to Weil-Malherbe and Dickens 206 the rate of elimination of 

 3,4-benzpyrene is affected by the solvent employed; the incidence of 

 sarcoma was found to be dependent upon the rate of absorption. When 

 the carcinogen was dissolved in synthetic tricaprylin in the presence of 

 cholesterol, a higher rate of elimination and a higher tumor incidence 

 were found to occur in mice. In the presence of phospholipids, a slower 

 elimination of the carcinogen occurred, and the latent period of the sar- 

 comas was extended. In a later study, 206 it was found* that not only 

 cholesterol, but also cholestanol, sitosterol and a-tocopherol caused 

 acceleration of the elimination rate of 3,4-benzpyrene; on the other hand, 

 ascorbyl palmitate had an inhibitory effect on the elimination of the ad- 

 ministered carcinogen. Epicholestanol, coprostanol, epicoprostanol, stig- 

 masterol, 7-dehydrocholesterol and ergosterol were found to be inactive. 

 Dickens and Weil-Malherbe 207 suggest that high tumor incidence is pri- 

 marily connected with the rate of oxidative metabolism of the carcinogen. 

 The higher the rate of metabolism, the greater the carcinogenic action. 

 A high rate of metabolism is directly related to the rate of elimination. 

 Fat itself when used as a solvent for the subcutaneous injection of car- 

 cinogens may inhibit carcinogenesis, 207,208 although the anticarcinogenic 

 action of mouse fat was shown to be lost after three years of storage. 207 

 Peacock and Beck 208 attribute the anticarcinogenic action of fat to an 

 increased rate of elimination of the carcinogen. 



Peacock 209 noted that, after the injection of the carcinogenic agents, 

 3,4-benzpyrene and methylcholanthrene, or of the non-carcinogenic com- 

 pound, anthracene, into rabbits, guinea pigs, fowl, or mice, these agents 

 are eliminated in the bile as fluorescent compounds or occasionally in the 

 feces in unchanged form. Chalmers 210 proved that the bile, feces, and 

 urine of mice contain a fluorescent compound, called BPX, after the 



206 H. Weil-Malherbe and F. Dickens, Cancer Research, 6, 171-178 (1946). 



206 H. Weil-Malherbe, Biochem. J., 42, xxxiii (1948). 



207 F. Dickens and H. Weil-Malherbe, Biochem. J., 39, xxxix (1945). 



208 P. R. Peacock and S. Beck, Brit. J. Exptl. Pathol, 19, 315-319 (1938). 



209 P. R. Peacock, Brit. J. Exptl. Pathol, 17, 164-172 (1936). 



210 J. G. Chalmers, Biochem. J., 32, 271-278 (1938). 



