276 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



nally, Lundbaek and Maal0e 163 were unable to detect absorption of liquid 

 paraffin when it was injected, in an emulsified state, into the duodenum 

 of rats fasted for twenty-four hours. Among the earlier workers, Bradley 

 and Gasser 164 Avere the only ones to express the opinion that paraffin oil 

 can be absorbed if it is well emulsified. In spite of these findings, the 

 general opinion held until recently has been that hydrocarbons cannot 

 be absorbed. 



More recent work has forced a revision of our concepts on this subject. 

 One is forced to conclude from the results of Channon and his collabora- 

 tors 165_lfi7 that small amounts of the paraffins can be absorbed and de- 

 posited in the tissues. Thus, it was shown that liquid paraffins were 

 absorbed from the gastrointestinal tract of the rat and the pig, as demon- 

 strated by the small but unmistakable increase in the non-cholesterol frac- 

 tion of the unsaponifiable extract of liver fat after paraffin oil was included 

 in the diet. 166 The experiments demonstrate the role of the liver in stor- 

 ing unsaponifiable substances. That this positive result was not to be 

 attributed to the polycyclic nature of the paraffin hydrocarbons was 

 demonstrated by El Mahdi and Channon, 167 who obtained a similar result 

 with a purified synthetic n-hexadecane (CH 3 (CH 2 )i 4 CII 3 ), in the rat. 

 Channon and Devine 165 were likewise able to duplicate this result with 

 purified hexadecane in the cat; moreover, they succeeded in isolating 

 the hydrocarbon from the omentum, perirenal fat, muscle, and skin, 

 although they were unable to prepare it from the liver, where it was 

 probably present only in traces. The experimental evidence of Channon 

 and co-workers that hydrocarbons are absorbed has been given strong 

 support by the findings of Stetten. 168 Thus, it was noted that, when n- 

 hexadecane into which deuterium had been incorporated was fed to rats 

 in doses of 83 mg.'day, it was very efficiently absorbed from the gastro- 

 intestinal tract, and was partially deposited as such in the tissue lipids. 

 It was likewise observed that the absorbed hexadecane was oxidized to 

 fatty acid in the body. Apparently this change takes place in the liver. 

 Additional confirmation of the absorption of liquid paraffin by rats has 

 been obtained in the experiments of Daniel, Frazer, French, and Sam- 

 mons. 169 When a 50% solution of liquid paraffin in olive oil was fed to 



163 K. Lundbaek and O. Maal0e, Acta Physiol. Scand., IS, 247-252 (1947). 



164 H. C. Bradley and H. S. Gasser, /. Biol. Chem., 11, xx (1912). 



165 H. J. Channon and J. Devine, Biochem. J., 28, 467-471 (1934). 



166 H. J. Channon and G. A. Collinson, Biochem. J., 23, 676-688 (1929). 



1S7 M. A. II. El Mahdi and TI. J. Channon, Biochem. J., 27, 1487-1494 (1933). 



168 De W. Stetten. Jr., /. Biol. Chem., 147, 327-332 (1943). 



169 J. W. Paniel, A. C. Frazer, J. M. French, and H. G. Sammons, Biochem. J., 54, 

 xxxvii-xxxviii ( 1 953 ) . 



