V. SPECIFICITY OF ACTION 351 



glucose. The slow rate of absorption of w?/o-inositol apparently precludes 

 the formation of any significant amount of liver glycogen when this com- 

 pound is fed to fasted ratsJ^ However, m?/o-inositol given either orally or 

 intraperitoneally does depress urinary ketone body excretion. This provides 

 additional evidence that m?/o-inositol is metabolized to carbohydrate or to 

 intermediates which are common to carbohydrate metabolic pathways. 

 Virtually nothing is knoA\Ti about the pathways by which the inositol 

 molecule is cleaved and converted to the carbohydrate-like products in 

 animal tissues. 



V. specificity of Action 



ARTHUR H. LIVERMORE 



There are nine theoretically possible isomers of inositol, differing only 

 in the steric arrangements of their hydroxyl groups. Determining the 

 specific steric configuration which is essential for vitamin activity in a 

 particular organism becomes, then, simply a matter of testing all the 

 available isomers of inositol on the organism in question. Only seven of the 

 nine possible isomers are kno^vn, but of those tested only one, m?/o-inositol, 

 has vitamin activity for all the inositol-requiring organisms which have 

 been found up to the present time. There are some organisms for Avhich 

 w;?/o-inositol is the only isomer which serves as a vitamin, and other organ- 

 isms for which other isomers have slight vitamin activity. 



The vitamin activity of w?/o-inositol for yeast was first demonstrated 

 in 1928 by Eastcott,^ and for mice in 1940 by Woolley.^ Following this, 

 Woolley determined the comparative vitamin activities of various inositols 

 and inositol derivatives for mice and yeast. The results of this investiga- 

 tion are summarized in Table IV.* Alopecia in mice was cured not only by 

 m?/o-inositol but also by phytin, the hexaphosphate of w?/o-inositol, and 

 by mytilitol, which has since been shown to be C-methylscyllitol.^ Other 

 inositol isomers were completely inactive for mice. The j^east Saccharo- 

 myces cerevisiae, on the other hand, utilized the mono- and tetraphosphate 

 esters to a small extent only and did not utilize phytin at all. Mytilitol 

 was much less effective as a growth stimulant than was m^/o-inositol. As in 

 mice, the other isomers of inositol which were tested had no vitamin 

 activity. 



' E. V. Eastcott, /. Phys. Chem. 32, 1094 (1928). 



2D. W. Woolley, Science 92, 384 (1940). 



3 D. W. Woolley, J. Biol. Chem. 140, 461 (1941). 



*T. Posternak, Bull. soc. chim. biol. 33, 1041 (1951). 



