METABOLISM 



during digestion and assimilation, even after a prolonged deficiency 

 of ribofiavine. This mobilisation was prevented by a deficiency of 

 aneurine or pantothenic acid. The amount of ribofiavine stored in 

 the liver also increased when the amount of protein (casein) in the 

 diet was increased ; about one-third of the increase could be accounted 

 for by ingestion of increased amounts of methionine and none by 

 ingestion of cystine. ^^ In confirmation of this result, A. V. Trufanov ^^ 

 found that, although the free ribofiavine in the livers of rats remained 

 unchanged in protein deficiency, the bound ribofiavine fell ; at the 

 same time, the urinary excretion increased. Liver and muscle tissue 

 from protein-deficient rats was incapable of synthesising flavine- 

 adenine dinucleotide. 



The changes that took place in the ribofiavine content of different 

 tissues with increasing age were studied by Murray et al.^^ In thirty- 

 day old rats, the muscle ribofiavine was fairly constant at 4-13 to 4-28 

 /Ltg. per g., but at sixty days lower values were obtained and at 360 to 

 500 days still lower values. Values for liver were more variable, and 

 at thirty days were about six, and at sixty days, about nine times as 

 high as in muscle. Blood values were still more variable, ranging from 

 o-i to 0-2 )Ltg. per g. 



Intravenously administered ribofiavine was rapidly excreted into 

 the small intestine of bilaterally nephrectomised rats ; ^^ excretion 

 through the bile was relatively unimportant. Ribofiavine was 

 rapidly destroyed in the isolated large intestine, but only slowly in 

 the isolated loop of the duodenum. Intravenously injected ribo- 

 fiavine was not destroyed or eliminated by rats without an intestinal 

 canal and both kidneys. Appreciable destruction occurred on incuba- 

 tion with liver, lung, heart, stomach and intestinal preparations.^^ 



Ribofiavine in Pregnancy and Lactation 



Pregnant women excreted less ribofiavine in the urine than did 

 non-pregnant women,^^ even when large doses (5 mg.) were injected 

 intravenously. After parturition, the excretion remained at a low 

 level, but increased, sometimes to the normal level, on administration 

 of a 5-mg. dose. The ribofiavine content of the placenta was not 

 increased by the intravenous injection of 5 to 25 mg. of ribofiavine a 

 few days or hours before parturition. 



The human placenta contained i-68 to 3-14 /xg. of ribofiavine per 

 100 g., and of this 40 to 55 % was present in the free state. ^'^ The 

 arterial and venous blood of the mother and the umbilical cord blood 

 contained about 60 jxg. per 100 ml., the value being increased to 150 

 fxg. per 100 ml. two to three minutes after the intravenous injection 

 into the mother of 30 to 50 mg. of the vitamin. The value fell to 



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