40 II. BIOSYNTHESIS 



used the same amount of glucose for fat synthesis, irrespective of whether 

 or not acetate was also present, rat slices transformed more glucose to fat 

 in the absence of acetate than was the case when the latter compound was 

 present. 



A species difference has likewise been noted m the effect of x-rays. 

 Thus, while treatment with x-rays augmented fat synthesis in the rat liver, 

 it was without effect in this organ in the mouse. ^^^ This species difference 

 in response to lipogenesis is in agreement with the observation that no in- 

 crease in size of the liver occurs in the mouse following x-ray treatment, 

 while this organ is enlarged in the rat. 



e. The Effect of Vitamins. Vitamins of the B-complex are the ones 

 primarily concerned with fat synthesis. Of these, thiamine is believed to 

 play one of the most important roles. Thus, McHenry and Gavin, ^'^^•"^ 

 on the basis of earlier work of Ansbacher et a/.,^^" and of Bender and 

 Supplee,^^^ reported that thiamine, riboflavin, and rice polishings (vitamin 

 Be) exert associated effects upon the amount of body fat laid down by rats 

 and pigeons."^ Thiamine was shown to be the most important of the 

 three vitamins.'''^ Boxer and Stetten^^'^ likewise showed that rats on an 

 mirestricted diet formed more fat than did those which received a thiamine- 

 free diet ad libitum. However, when the fat formation of control rats re- 

 ceiving a complete diet but restricted in quantity to that consumed by the 

 rats on the thiamine-deficient regimen was compared no difference in the fat 

 content of the rats was noted. Boxer and Stetten^" conclude that the failure 

 of rats on a thiamine-deficient diet to form fat is attributable chiefly to the 

 diminished food intake, rather than to any specific action of the vitamin. 

 Gruber^^^ was unable to demonstrate any variation in fat synthesis in 

 pigeons which were force-fed, irrespective of whether or not the birds 

 received thiamine. 



Carter and Phizackerley^^^ reported that a deficiency of pyridoxine in the 

 rat results in a decrease of the total lipid content of the body, and a diminu- 

 tion in the amount of neutral fat in the liver. The proportion of fat in the 

 tissues can be restored on the pyridoxine-free diet by feeding this foodstuff. 

 These workers conclude that the results are consistent with the view 

 that the deficiency of pyridoxine involves an inability on the part of the rat 

 to convert carbohydrate to fat. 



"8E. W. McHenry and G. Gavin, J. Biol. Chem., 125, 65.3-660 (1938). 



1" E. W. McHenry and G. Gavin, J. Biol. Chem., 128, 45-49 (1939). 



180 S. Ansbacher, G. C. Supplee, and R. C. Bender, /. Nutrition, 11, 401-409 (1936). 



1" R. C. Bender and G. C. Supplee, /. Am. Chem. Soc, 59, 1178-1182 (1937). 



182 M. Gruber, Biochim. et Biophys. Acta, 7, 480-481 (1951). 



183 C. W. Carter and P. J. R. Phizackerley, Biochem. J., 49, 227-232 (1951). 



