180 III. OXIDATION AND METABOLISM 



suppression of ketosis is ketolytic. The explanation, based upon the 

 incorporation of ketone bodies via active acetate into the tricarboxylic 

 acid cycle, is practically identical with the original concept of Shaffer.-''^ 

 The only variation is that Shaffer believed that the coupled reaction was 

 between acetoacetate and a triose, while the current concept is that the 

 coupling occurs between active acetate (formed from ketone bodies) and 

 oxaloacetate. 



f. The Comparative Ketolytic Effect of the Sugars. Although it would 

 be expected that the ketolytic effect of sugars and of glucose intermediates 

 would be in proportion to the D-glucose derived from the compound in 

 question, galactose presents an interesting exception. Galactose is a sugar 

 more difficult to metabolize than is glucose, since the galactosemia following 

 galactose feeding is greater than the corresponding hyperglycemia after 

 equivalent amounts of glucose have been given.^^^ Moreover, a galacto- 

 suria follows even moderate doses of galactose in the normal animal, 

 while much larger amounts of glucose will not produce any detectable 

 glycosuria. 



In spite of the apparently difficult metabolism of galactose, it has 

 repeatedly been demonstrated to have a greater ketolytic activity than 

 has glucose. Thus, when given to fasting men or women or to men 

 presenting a ketonuria produced by the ingestion of a protein-fat 

 diet,^^'' the ketonuria was reduced to lower values, and the minimum 

 level was attained at a longer period after the ingestion of this sugar than 

 was the case when glucose was taken. In a typical experiment on a fasting 

 man, the minimum ketonuria was obtained twenty hours after glucose 

 and twenty-five hours after galactose had been taken, when 72 g. of the 

 sugars were ingested ; the resumption of the preprandial level of ketonuria 

 occurred forty-four hours after the administration of glucose, but not until 

 sixty-eight hours after that of galactose. In this experiment, the values 

 for ketone body excretion during the period of maximum ketolysis were 

 0.260 g./8 hr. in the glucose test, and 0.201 g./8 hr. in the galactose experi- 

 ment. ^^° Butts^^'' reported a similar phenomenon in rats, in which an 

 exogenous ketonuria was produced by the administration of sodium 

 acetoacetate twice daily. Moreover, the latter investigator demonstrated 

 that the nitrogen-sparing action of glucose and galactose was in line with 

 the ability of the animal to reduce ketonuria. As a possible explanation 

 for these findings, Deuel et al}^^ noted that the liver glycogen of dogs and 

 of rats was higher six hours after the ingestion of glucose than following 



"6 M. Wierzuchowski, W. Pieskow, and E. Owsiany, Biochem. Z., 230, 146-172 (1931). 



