BIOTIN 547 



effective as ( + ) biotin. The lower figure was obtained for near maximal 

 response of the organism, whereas the higher value represents the relative 

 efficiency in eliciting a suboptimal response. Hence, in plots of dose- 

 response for the rat, the general shape of the curves for oxybiotin and 

 biotin differ. 



As little as 8 y of DL-oxy biotin injected intramuscularly in chicks 

 (White Leghorn cockerels) rendered deficient in biotin by supplementing 

 a biotin-deficient diet with raw egg white caused the disappearance of 

 the mandibular lesions within a week, and some healing of the feet. 

 After three weeks, the hard, scaly, cracked skin of the bottom of the 

 feet sloughed off, leaving normal tissue; but edema was still evident in 

 some segments of the toes of the chicks. No deficiency symptoms of 

 chicks on a biotin-deficient diet were obtained if a supplement of oxy- 

 biotin was provided; chicks becoming deficient on the diet were cured 

 by oxybiotin. Injected intramuscularly, DL-oxybiotin was approximately 

 17 per cent as active as ( + ) biotin in eliciting growth response of day- 

 old chicks maintained for one week on a biotin-deficient diet containing 

 raw egg white. The plots of dose-response for both compounds are similar 

 in shape. 29 



These results contrast sharply with those of another group, 30 who 

 report that the oxygen analogue, when administered as a supplement in 

 the diet instead of being injected intramuscularly, fails to replace biotin 

 completely for growth of the chick (White Leghorn cockerels) on a 

 biotin-deficient diet. It is reported that the racemic analogue at 20 y per 

 100 g of diet is approximately 20 per cent as active as ( + ) biotin in 

 promoting growth, but at high concentrations of the analogue in the diet 

 it is only 0.5-3 per cent as effective as biotin. The relative activities are 

 reported to vary inversely with the amount of analogue fed. Since optimal 

 growth as obtained with biotin was not attained with any concentration 

 of the analogue up to 1000 y per 100 g of diet, it was suggested that the 

 analogue fulfilled only a part of the function of biotin in the chick. The 

 oxygen analogue is reported to have about one-third the activity of 

 biotin in curing the dermatitis which develops in the deficient animals. 

 It will be interesting indeed if the activity of oxybiotin (O-heterobiotin) 

 can be demonstrated to be dependent upon the method of administration 

 to the chick. 



Although several analogues which were very active in replacing the 

 corresponding vitamins had previously been prepared and tested, the 

 oxygen analogue of biotin afforded the first opportunity for development 

 of specific assays useful in determining whether the analogue was con- 

 verted into the vitamin or was utilized as such by organisms in which 

 it had vitamin activity. Two direct assays for oxybiotin have been 



