VITAMINS 



CHOLINE 



253 



Physiological function 



A lack of choline in the diet of young, rapidly growing rats results in 

 the accumulation of excessive amounts of fat in the liver. There may 

 also be damage to the kidneys, which become discolored from internal 

 hemorrhage. The "fatty livers" are restored to normal by feeding small 

 amounts of choline or of methionine. On the other hand, feeding choles- 

 terol aggravates the condition. Older rats are much less likely to suffer 

 from the symptoms of choline deficiency. 



It is supposed that the fatty deposits in the liver are caused partly 

 by a failure of fat transport and partly by a decrease in the normal 

 rate of fat catabolism (that is, transformation into other simpler ma- 

 terials) in the liver. The evidence at present available is consistent with 

 the assumption that neutral fat (that is, glycerides) must be converted 

 into phospholipides before it is transported elsewhere in the body or, if 

 it remains in the liver, before it is catabolized. Since choline is one 

 component of the lecithin type of phospholipides, it would obviously be 

 needed for these purposes. In fact, it has been possible with the aid of 

 radioactive phosphorus to follow the rate of "phospholipide turnover" 

 in the liver, that is, the rate at which phospholipide molecules are formed 

 and removed, and to demonstrate that choline increases this rate. The 

 effect was observed within one hour and was proportional to the amount 

 of choline fed. 



Choline is also required for the normal nutrition of chicks and of 

 young turkeys. In conjunction with manganese it prevents the develop- 

 ment of a disease of chickens known as perosis, in which the leg tendon 

 slips off from the hock joint as a result of malformation of the bone, and 

 the bird is consequently unable to walk. Normal egg production by 

 chickens is also impaired by a lack of sufficient choline in the diet. 



One of the main metabolic functions of choline is to supply "labile" 

 methyl groups for various transmethylation reactions. These are de- 

 scribed in Chap. 13. 



Chemical nature 



Choline is a very strong base, with the followmg structural formula: 



CH3 

 HOCH2-CH2— N— CH3 

 HOCH5 



Choline 



