VITAMINS 



373 



VITAMINS 



apolis, Burgess Publishing Co., 1950, 

 115 pp.; The Association of Vitamin 

 Chemists, Inc., Methods of Vitamin 

 Assay, New York; Interscience Pub- 

 lishers, Inc., 1947, 189 pp.; Johnson, 

 D. C, Methods of Vitamin Determina- 

 tion, Minneapolis, Burgess Publishing 

 Co., 1949, 109 pp. 

 A. Growth promoting, anti-infective and 

 anti-xerophthalmic vitamin, a polyene 

 alcohol. There are also vitamins A2, 

 A3 and the so-called Sub-vitamin A, 

 and neo-vitamin A, which is a sterioiso- 

 mer of vitamin A. The members of 

 the vitamin A group differ in their 

 maximum absorption in the ultraviolet. 

 Provitamins A are alpha, beta and 

 delta carotene which vary in their 

 vitamin A activity. Vitamin A can 

 be determined by the following methods : 



1. Its absorption at 326 m^ measured 

 by a spectrophotometer, or photoelec- 

 tric spectrophotometer, under con- 

 trolled conditions of analysis. 



2. The glycerol dichlorohydrin 

 method of Sobel, A. E. and Werbin, 

 H., Ind. Eng. Chem., Anal. Ed., 1946, 

 18, 570-573; 1947, 19, 107-112. 



3. The Carr-Price reaction which 

 employs the antimony trichloride re- 

 agent. This reaction has been applied 

 to determine the vitamin A content 

 of hepatic mitochondria of rats after 

 separation by differential centrifuga- 

 tion. The mitochondria contain 249 

 to 910 U.S. P. units of vitamin A per 

 100 mg. mitochondrial lipid (Goerner, 

 A. and M. M., J. Biol. Chem., 1937- 

 38, 122, 529-538; 1939, 128, 559-565). 

 This test has also been employed for 

 vitamin A in serum, the colors being 

 checked against alizarin solutions (Par- 

 ker, R. C, Methods of Tissue Culture, 

 New York: Hoeber, 1938, 292 pp.). 

 According to Joyet-Lavergne, P., C. 

 rend. Acad. d. Sci., 1935, 201, 1219-1221, 

 vitamin A can be demonstrated in the 

 red blood cells of rays (marine fish) by 

 the Carr-Price test. This same investi- 

 gator has also applied the Carr-Price 

 reaction to a variety of tissues of sev- 

 eral animals, and has found that in 

 every case the mitochondria appear as 

 bright blue bodies (Ann. physiol. physi- 

 cochem. biol. 1937, 13, 1019-1021), see 

 also Bourne, G. Austral. J. Exp. Biol. 

 Med. Sci. 1934, 13, 239-249. The Carr- 

 Price reaction can localize vitamin A 

 precisely in individual mitochondria 

 according to Jones, J., Lab. Clin. 

 Med., 1947, 12, 700. 



4. Fluorescence microscopy. The 

 fading green fluorescence of vitamin A 

 is used by Popper for the identification 

 and localization of vitamin A in cells 

 (Gyorgy, 1950, p. 89). Tissues are 



fixed in 5% formalin and examined as 

 soon as possible. Human tissues are 

 kept in the fixitive not longer than 18 

 hrs. and animal tissues not longer than 

 8 hrs. Why this difference should be 

 is not clear. Frozen sections are made, 

 mounted in water and examined at 

 once with a fluorescence microscope. 

 Any green fading fluorescence is con- 

 sidered to be vitamin A and is usually 

 located in fatty material. For a more 

 exact localization of this vitamin, 

 sections may be stained with 1% aq. 

 methylene blue for 30 sec. This stain 

 interferes only slightly with the vita- 

 min A fluorescence. By Popper's 

 method vitamin A has been found in 

 the liver, adrenal cortex, testicle, and 

 in the ovary where it undergoes charac- 

 teristic changes during the mentrual 

 cycle and during pregnancy. It is also 

 present in the intestinal tract during 

 absorption, in lactating breasts, in 

 the retina and in certain pathologic 

 conditions of the kidney. For a re- 

 view of its distribution in tissues, see 

 Popper, H., Physiol. Rev., 1944, 24, 

 205-224. According to Popper caro- 

 tene can be differentiated from vitamin 

 A by its very slowly fading green 

 fluorescence, and anhydro- or "cy- 

 clized", vitamin A may be recognized 

 by its dark brown fluorescence, which 

 gradually becomes dull green and fi- 

 nally fades out entirely. 



B. Complex contains inany factors. 



Bi. Thiamine hydrochloride (anti-neuritic 

 factor, aneurin). Thiamine can be de- 

 termined colorimetrically by the 

 method of Hochberg, M., Melnick, D. 

 and Oser, B. L., Cereal Chem., 1945, 

 22, 83-90. This vitamin can also be 

 determined microbiologically using 

 Streptococcus salwarius, or Lactobacillus 

 fermenti 36 (Gyorgy, 1950, pp. 372-376). 

 The coenzyme derived from thiamine 

 is thiamine pyrophosphate. It is in- 

 volved in the decarboxylation of alpha 

 keto acids, particularly pyruvic acid, 

 and consequently in the tissue oxida- 

 tion of carbohydrates. In thiamine 

 deficiency the pyruvate and lactate 

 blood levels are increased, the increase 

 in the former being due to a lack of 

 ability to change pyruvate to lactate 

 without thiamine. No histochemical 

 method is available for this vitamin. 



B2. Vitamin G (Riboflavin, Lactoflavin). 

 Riboflavin can be determined chemi- 

 cally by measuring its fluorescence in 

 light of wave length 440 to 500 mn 

 (Gyorgy, 1950, pp. 102-144). Ribo- 

 flavin can also be determined polaro- 

 graphically in pure solutions. The 

 flavoproteins catalyze the metabolism 

 of such substances as D-amino acids, 



