The absorption of n-hexadecane from the alimentary tract of the rat

THE degree to which unsaponifiable substances are absorbed from the alimentary tract has assumed considerable importance in the last few years on account of the biological significance of the fat-soluble vitamins and carotene. In previous papers the absorption of squalene, phytol, oleyl and cetyl alcohols, cholesterol and a medicinal liquid paraffin has been investigated [Channon, 1926; Channon and Collinson, 1928; 1929]. In the last case, it was found that the liquid paraffin was absorbed to some extent by the rat. Further, from consideration of the cholesterol content of the liver unsaponifiable fractions and of the iodine values of the non-sterol portion of those fractions, it was deduced that the liquid paraffin was present in the liver. By further experiments on pigs, it was found possible chemically to isolate the paraffin from the liver of that animal. These results were of interest because firstly they demonstrated the absorption of hydrocarbons from the alimentary tract to a limited extent at least, even though previous investigations had led to the current view that such hydrocarbons were not absorbed, and secondly they focused attention on the apparent role of the liver in storing unsaponifiable substances generally. Demonstration of the former fact raised the question as to the mechanism whereby such inert substances as hydrocarbons are absorbed. Since chemical investigation of the liquid paraffin used showed that it consisted of a mixture of polycyclic hydrocarbons, it was feit that the positive results obtained for its absorption, which seemed at variance with previous work, might be attributable to its particular chemical nature. For this reason, it was deemed necessary to carry out further work using a synthetic normal hydrocarbon.