320 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



exposure to 025 r. After an interval of ten hours, little difference in ab- 

 sorption could be noted between the irradiated and the control rats. How- 

 ever, the distribution of vitamin A in the tissues was modified by \-irradia- 

 tion. Smaller amounts of vitamin A were found in the liver and larger 

 quantities in the carcass. 



(c) The Stability of Vitamin A in the Intestine. Although Baumann 

 and associates 459 found that vitamin A ma}' be largely destroyed in the 

 gastrointestinal tract, Reifman and co-workers 418 were unable to demon- 

 strate any appreciable destruction in three-hour tests. Moreover, Richard- 

 son 4 ' 10 has indicated that the putrefaction in fish livers is without a marked 

 effect on their vitamin A content. Geiger 461 also reported that no caro- 

 tene or vitamin A is destroyed by intestinal bacteria over a twenty-four- 

 hour period. Bieri 462 found that vitamin A acetate was stable for twenty- 

 eight days in aqueous solutions either in Tween 40 (polyoxyalkylene 

 derivative of sorbitan monopalmitate), or Tween 80, irrespective of 

 whether it was stored under air or nitrogen. On the other hand, /3-caro- 

 tene remained unchanged only in Tween 40 and under nitrogen. 



The tocopherols are now recognized to be the most important stabilizing 

 agents for vitamin A and carotene. Bacharach, 463 Moore, 333 and Davies 

 and Moore 334 were the first to demonstrate the synergistic action of toco- 

 pherols on the deposition of vitamin A in the tissues. It was later shown 

 by Hickman and associates 464 ' 465 that the growth-promoting effect of vita- 

 min A alcohol, vitamin A acetate, and U.S. P. vitamin A reference oil was 

 enhanced when natural vitamin E preparations (mixed tocopherols) 

 were present. This "sparing" or "synergistic" action of the tocopherols 

 is termed "co-vitamin E" activity. 465 The co-vitamin E action on vita- 

 min A has been confirmed by a number of workers, including Gridgeman, 466 

 Guggenheim, 343 Lemley et a/., 467 Sanders and co-workers, 468 and most 

 recently by Galeone and, San Lorenzo. 46 " 



459 C. A. Baumann, B. M. Riising, and H. Steenbock, ./. Biol. Chem., 107, 705-715 

 (19:-J4). 



"■" A. Richardson, Personal communication, 1952. 



461 E. Geiger, Personal communication, 1952. 



462 J. CI. Bieri, ./. Nutrition, 44, 327-334 (1951). 



463 A. L. Bacharach, Quart. J. Pharm. Pharmacol,, 18, 138-149 (1940). 



464 K. C. D. Hickman, P. L. Harris, and M. R. Woodside, Nature, 150, 91-92 (19421 

 456 K. C. D. Hickman, M. W. Kaley, and P. L. Harris, J. Biol. Chem., 152, 303-311 



(1944). 



466 N. T. Gridgeman, The Estimation of Vitamin A, 2nd ed., Lever Bros. & Unilever, 

 Port Sunlight, Cheshire, 1-74 (1945), p. 37. 



467 J. M. Lemlev, It. A. Brown, O. D. Bird, and A. D. Emmett, J. Nutrition, 84, 205- 

 218(1947). 



468 R. Sanders, A. Beaty, and M. Dodd, Abst. Meetings, Am. Chem. Soc, Div. Biol. 

 Chem., Cleveland, April 4* 1944, 17B. 



469 A. Caleone and G. San Lorenzo, Intern. Z. Vitaminforsrh., 19, 257-265 (1948). 



