The Absorption of Fatty Esters in the Mouse Intestine

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Abstract
The foregoing experiments have emphasized several facts quite clearly. The methyl esters of the higher fatty acids are not emulsified to any extent in the intestine of the fasted mouse. The addition of small amounts of corn oil (triglyceride) or monopalmitin (a monoglyceride) promotes the emulsification. The intestinal absorption of fatty esters has been found to be subnormal in the fasted mouse and to be brought to normality by the addition of corn oil. It has also been found to be normal in the animal on a fat-free diet, indicating that substances in the diet other than glycerides may promote emulsification. Emulsion formation and absorption have been more closely correlated in an experiment in which both types of information are given for the same animal. Emulsion formation is evidently necessary for optimum absorption. The data do not necessarily support Frazer's theory of particulate absorption as opposed to the lipolytic theory propounded by Verzar ('48), since emulsification would also favor the action of lipase. However, it can now be stated with more confidence that glycerides are important factors in the emulsification and absorption of fatty substances in vivo. Several results from the literature may also lend themselves to further clarification. Among these are the papers of Barnes, Miller, and Burr ('41a, b, c) who found the rate of absorption of the methyl esters of the conjugated fatty acids of corn oil and that of corn oil itself to be different. The same authors found fat absorption in essential fatty acid-deficient and adrenalectomized animals to be normal. However, in each experiment, methyl esters were administered to animals which had been fasted 18 hours. It is possible that in all cases both the controls and the experimental animals were not carrying on normal fat absorption. Finally, although Frank (1898) found complete hydrolysis of esters, this may have been because adequate emulsification could not occur and absorption had taken the alternate pathway proposed by Frazer (hydrolysis, following by absorption into the portal system). Further experiments along lines are in progress and may serve to elucidate the general mechanism of fat absorption more completely.