RIBOFLAVINE 



suggested that photolysis of riboflavine with precipitation of the 

 sparingly soluble lumiflavine may be a factor in the mechanism. 



Riboflavine has also been shown to be present in the retinal pigment 

 of the human eye, where it appears to play a role in light adaptation 

 similar to that of rhodopsin in dark adaptation.''^ Apparently, it 

 has the property of transforming rays of short wave-length into 

 yellowish-green fluorescent light, for which the sensitivity of the eye 

 is maximal. It also protects the cones of the retina against excessive 

 light. Riboflavine is not re-synthesised in the absence of oxygen, 

 and the ocular manifestations of aribofiavinosis are due to the in- 

 ability of the body to make good the losses of riboflavine that occur on 

 exposing the eye to light. 



Riboflavine and Liver Damage 



Normally, when liver slices were incubated with a natural or 

 synthetic oestrogen, the activity of the latter was destroyed. The 

 livers of rats reared on a vitamin B-deficient diet, however, were 

 unable to effect this inactivation, but recovered the power of in- 

 activating oestrone and oestradiol when aneurine or riboflavine was 

 added to the diet ; '^ pyridoxine, pantothenic acid, biotin and choline 

 were ineffective in this respect. Even aneurine and riboflavine, 

 however, did not restore the ability of the liver to inactivate stil- 

 boestrol. No explanation has been put forward to account for these 

 observations, although, from the fact that administration of methionine 

 also restored the oestrogen-inactivating properties of the liver, it may 

 be concluded that a deficiency of riboflavine and aneurine leads to a 

 failure of liver function. 



An observation, perhaps connected with the foregoing, was made 

 by W. Antopol and K. Unna,^^ who showed that administration of 

 large amounts, e.g. lo mg. three times per week, of riboflavine retarded 

 the onset of pathological changes in the liver of rats promoted by 

 the feeding of _^-dimethylaminoazobenzene ; nicotinic acid had no 

 effect. 



References to Section 15 



1. O. Warburg and W. Christian, Biochem. Z., 1931, 242, 206 ; 1932, 



254, 438 ; 1933, 267, 492 ; 1933. 263, 228 ; 1933, 266, 377 ; 

 Naturwiss., 1932, 20, 688, 980. 



2. H. Theorell, Biochem. Z., 1934, 276, 37, 344 ; 1935, 278, 263. 



3. F. Weygand and H. Stocher, Z. physiol. Chem., 1937, 247, 167. 



4. F. Weygand and L, Birkofer, ibid., 1939, 261, 172. 



5. H. Theorell, Biochem. Z., 1935, 278, 279. 



6. R. A. Kekwick and K. O. Pederson, Biochem. J., 1936, 30, 2201. 



200 



