610 



BIOTIN 



The biotin oontent of fetal tissues increases rapidly during the last stage 

 in pregnancy. In rats the adjustment to adult levels takes place during the 

 last 2 to 3 days of pregnancy. The concentration of biotin in the fetuses, 

 which in rats was found to be 0.02 7 per gram of fresh tissue on the thir- 

 teenth day of pregnancy, increased fivefold prior to parturition." 



The low biotin content in immature tissues, such as fetal (^r tumor tissue, 

 aroused the interest of several workers as to the possible relation of bio- 

 tin to tumor growth as such. Du Vigneaud and his associates'^ studied 

 the effect of biotin on the production of primary hepatoma in rats fed 

 1 ,1-N-dimethylaminoazobenzene (butter yellow). It had previously been 

 shown that various dietary factors, such as riV^^flavin and high protein 

 intake, may exert a protective effect on the lixer in rats receiving the car- 



TABLE XIII 



Comparative Values on the Biotix Context" of Adult, Embryo, and Tumor 



Tissues According to West and Woglom^* 



" Biotin values given in milligrams per gram of dry tissue. 



* Rabbit papillomas. 



"" Rabbit skin carcinomas. 



cinogen butter yellow. Du \"igneaud and his associates found that the 

 addition of pure biotin to such highly protective rations caused a higher 

 incidence in tumor formation. Thus biotin, under the experimental condi- 

 tions chosen, seemed to exert a procarcinogenic effect. It was then suggested 

 that biotin deficiency induced by avidin, the egg wliite iiijuiy factor, might 

 be of some therapeutic value on cancer. 



In later studies, this assumption was not l)orne out l)y animal c\{)ciimonts 

 or by observations on human patients. 



Even the original findings on the effect of l)iotiii in rats fed butter yellow 

 could not be duplicated.'^' ^" .Admittedly, egg white appeared to afford 

 some protection against hejiatoma formation duo to l)uttcr yellow, liias- 



" H. Lewis and (i. Everson, ./. Nidrilion 46, 27 (1952). 



"V. du Vigneaud, J. M. Spangler, D. Burk, C. J. Keiislcr, K. Suguiia, and ('. P. 



Rhoads, Science 95, 174 (1942). 

 '^ P. Gyorgy, Unpublished ol)serva(i()ns. 

 «<> B. E. Kline, J. A. Miller, and H. !'. Husch, ('dtirer />V,sra/r/? 5, ()41 (1945). 



