44 II. BIOSYNTHESIS 



glycerol moiety in the triglyceride molecule has not been considered by 

 most biochemists as posing any particular difficulty. 



The earlier literature furnishes considerable information to indicate that 

 glycerol is readily transformed to glucose in the animal body. Since the 

 reactions involved in such transformations are reversible, it is believed that 

 this proof likewise constitutes evidence for the reverse reaction, namely 

 glucose — >■ glycerol. 



As early as 1902, Cremer^^^ demonstrated that as much as 40% of in- 

 gested glycerol could be accounted for as "extra glucose" in the urine of the 

 phlorhizinized dog; Liithje^"" obtained similar results with depancreatized 

 dogs. On the other hand, Chambers and DeueP"^ were able to recover 

 practically all of the administered glycerol in the urine of fasting phlo- 

 rhizinized dogs as "extra glucose." It is now generally considered that 

 this transformation is a quantitative one. 



The glycerol — >- glucose reaction has been directly demonstrated by an- 

 other procedure, namely by the isolation of an increased glycogen deposition 

 following the administration of the trihydric alcohol. This conversion was 

 first reported by Catron and Lewis, ^"^ and was confirmed by Shapiro.^''* 

 Although Deuel and associates'"^ were unable to demonstrate a conversion 

 of the glycerol of common fats to glycogen in rats, they did prove that the 

 glycerol of triglycerides such as triacetin, tributyrin, tricaproin, and tri- 

 caprylin, which cannot be deposited in the fat depots, gives rise to glycogen. 



The conversion of glycerol to glucose has been indicated by a number of 

 indirect procedures. Thus, Voegtlin et alr^'-' found that glycerol will re- 

 place glucose in relieving the hypoglycemic and other toxic effects of in- 

 sulin injections. On the other hand, Mann and Magath'"^ were unable to 

 maintain the blood sugar level of the hepatectomized dog by the admin- 

 istration of glycerol, except for a transitory period ; hence, it was considered 

 that the liver is essential for the storage of glucose and the transformation 

 of glycerol to glucose. 



"» M. Cremer, Miinch. med. Wochschr., 49, 944 (1902). 



200 H. Luthje, Deut. Arch. klin. Med., 80, 98-104 (1904). 



2o» W. H. Chambers and H. J. Deuel, Jr., /. Biol. Chem., 65, 21-29 (1925). 



202 L. F. Catron and H. B. Lewis, /. BM. Chem., 84, 553-559 (1929). 



203 1. Shapiro, /. Biol. Chem., 108, 373-387 (1935). 



20* H. J. Deuel, Jr., J. S. Butts, H. Blunden, C. H. Cutler, and L. Knott, /. Biol. Chem., 

 117, 119-129 (1937). 



206 C. Voegtlin, E. R. Dunn, and J. W. Thompson, Am. J. Physiol, 71, 574-582 (1924- 

 1925). 



206 F. C. Mann and T. B. Magath, Arch. Internal Med., SO, 73-84; 171-181 (1922); 

 31, 797-806 (1923). 



