b9b VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



e'. Effect on the Transformation of Sorbitol to Glucose: Johnston and 

 Deuel 913 reported that the ketolytic effect of the hexitol, sorbitol, is only 

 about 25% of that of glucose when tested with endogenous ketonuria, while 

 a figure of 50% of the potency of glucose was noted when the tests were 

 based upon exogenous ketonuria. Since glycogen was found to be higher 

 in the liver and lower in the muscle following the administration of sorbitol 

 than after that of glucose, it was postulated that the liver is probably the 

 site for the conversion of sorbitol to glucose. These authors state: "The 

 lower effect of sorbitol in endogenous compared with exogenous ketonuria 

 is believed to be caused by the failure of the fatty liver to convert sorbitol 

 to glycogen at its normal rate, owing to a derangement in its function in 

 animals with fatty livers." 



It is apparent from a consideration of the reactions of fatty livers when 

 tested by some common physiologic procedures that the dietary fatty livers, 

 as well as those arising from hepatic poisons, are abnormal. The extent 

 to which abnormalities in metabolism will occur would be expected to in- 

 crease as the proportion of liver fat becomes greater. However, the de- 

 velopment of one function, namely that of producing a ketonuria, does not 

 change with a further increase in liver lipids after a moderate fatty infiltra- 

 tion has occurred. 



f . Effect on Uric Acid Oxidation: In contradistinction to the higher 

 primates and man, the dog possesses the enzyme, uricase, present in the 

 liver. Consequently, instead of uric acid being the ultimate product of 

 purine metabolism, as it is in man, this substance is oxidized to allantoin in 

 the dog; this is, in turn, excreted in the urine. 



Some years ago it was demonstrated by Bollman, Mann, and 

 Magath, 914,915 at the Mayo Clinic, that uric acid appears in the blood and 

 urine of the dog following hepatectomy. A similar phenomenon has re- 

 cently been observed by Groen, 916 as a result of liver damage following 

 fatty infiltration. Nine dogs were fed exclusively bacon for a period of 

 months. This diet provoked the production of fatty livers. Of the nine 

 dogs, seven died within a relatively short period. Postmortem examination 

 revealed the presence of uric acid stones in the kidneys, bladders, and 

 ureters of these dogs. The author suggests that the continued presence of 

 fat in the liver had produced a condition akin to "chemical hepatectomy." 



g\ Choline Synthesis and Destruction in the Liver: Barrenscheen and 



913 C. Johnston and H. J. Deuel, Jr., J. Biol. Chem., 149, 117-124 (1943). 



914 J. L. Bollman, F. C. Mann, and T. B. Magath, Am. J. Physiol, 72, 629-646 (1925). 



915 J. L. Bollman and F. C. Mann, Am. J. Physiol., 104, 242-246 (1933). 



916 J. Groen, Science, 107, 425-426 (1948). 



