Metabolism of l-ascorbic acid, dehydro-l'ascorbic acid, and diketo-l-gulonic acid in the guinea pig.

The interrelationships of L-ascorbic acid (AsA) and dehydro-L-ascorbic acid (DHA) have been investigated both in viva and in vitro by numerous workers, with especial emphasis upon the conversion of DHA to AsA by the animal body (l-8). The conversion of DHA to diketo-L-gulonic acid (DKA) in vitro has been shown by Herbert and coworkers (3), by Borsook (l), and by Penney and Zilva (6), and this conversion has been extensively studied in viva by Penney and Zilva. The method of analysis for DKA employed by the latter authors depended on the development of a color when alkali was added to the coupled product of DKA and 2,4-dinitrophenylhydrazine. In view of the fact that certain intermediary products of metabolism, such as pyruvic acid, ac-ketoglutaric acid, and oxalacetic acid, form derivatives with 2,4-dinitrophenylhydrazine which yield a similar color in alkali (9), it is apparent that large errors could result from the application of such a method to the determination of DKA in animal tissues. With the development in this laboratory of a method for the differential determination of AsA, DHA, and DKA in the same tissue filtrate (lo), it became possible to study more precisely the metabolism of each of these three compounds when injected into the guinea pig. By this method, data have also been obtained on the tissue levels of each of the compounds in normal guinea pigs and in guinea pigs fed a scorbutigenic diet for varying lengths of time.