304 ASCORBIC ACID 



stances. They contend that the production of collagen would occur more 

 rapidl}'' than it would in the healing wounds of normal animals because of 

 the accumulation of unset gel material. Ham and EUiott^^ maintained, how- 

 ever, that in the repair of skeletal tissues a completely new bone matrix 

 can form within 48 hours, and they stated also that they found no histo- 

 logical evidence to support the contention that the new dentine which forms 

 after administration of antiscorbutics represents the gelation of a previously 

 produced unset gel. They referred to the fact that Fish and Harris^"* found 

 no accumulation of fluid l)etween the pulp and dentine which would have 

 occurred had an unset gel been formed continuously during the scorbutic 

 period. From these facts they conclude that the evidence for the gelation 

 theory is inadequate. 



c. Mode of Action 



The chemical or physical means by which ascorbic acid exerts its con- 

 trolling influence is not understood. It may function as a catalyst^^- ''^' ^^"'^ 

 201 . 202 QY possibly as a component of other compounds. 



(1) Catalytic Action. On the basis of experiments which have been con- 

 ducted in vitro under conditions approximating those of the body, it would 

 appear that the vitamin could act directly upon the cells, thereby condition- 

 ing them to secrete the enzymes, or it could act directly on the intercellular- 

 matrix, creating conditions such as proper pH values and molecular ar- 

 rangements which would enable the enzymes to function; also it might act 

 by promoting conditions favorable to coupling processes such as establish- 

 ing linkages between proteins and carbohydrates. Such an activity could be 

 of particular importance at cell surfaces. The vitamin has in fact been shown 

 to have an effect upon the surface activity of colloidal solutions by Keller 

 and Kiinzel.^"^ They found that under certain conditions such as high di- 

 lution and a close approach to physiological pH values ascorbic acid can 

 alter surface active substances such as lecithin, either in the free form or 

 when combined with tissue protein. Results of recent studies-"'*"'-'^^ also 

 suggest the probability of a cell surface action of the vitamin. Harman and 

 Warren^* found that the cell walls in the embryos of scorbutic animals Avere 

 indistinct and blurred in appearance whereas they were well defined in the 

 corresponding tissues of normal animals indicating, differences in organiza- 

 tion and/or in the products of synthesis at cell surfaces. The rounding of 

 the special mesenchymal cells such as the fibroblasts is also an indication 



2«i S. B. Wolbach and O. A. Bessey, Physiol. Revs. 22, 233 (1942). 



202 B. Ekman, Acta Physiol. Scand. 8, Suppl. 22, 196 pp. (1944). 



203 C. J. Keller and (). Kiinzel, Z. ges. exptl. Med. 103, 704 (1938). 



204 F. Bernheim, M. L. C. Bernheim, and K. M. Wilbur, J. Biol. Chem. 174, 257 (1948). 

 206 M. E. Reid, Am. J. Botany 28, 410 (1941). 



206 E. H. Newcomb, Proc. Soc. Exptl. Biol. Med. 76, 504 (1951). 



