Intestinal absorption of cytidine diphosphate choline (CDP choline), its structural changes in the digestive tract, and hepatic uptake have been investigated in rats using 14C-labeled (14CH3 attached to N of choline) and 3H-labeled (at C5 of pyrimidine) compounds. The results indicate that: 1) CDP-choline is relatively stable in the stomach, but is quickly degraded into cytidine and choline in the intestine; 2) The hepatic uptakes of 14C and 3H reach the maximum in two to three hours after oral administration; 3) Whereas the amount of 14C remaining in the gut is inversely related to the hepatic uptake, no similar correlation is seen with 3H-labeled CDP-choline, and 4) Extrahepatic uptake of 14C and 3H is very small. The possibility of phosphorylation in the mucosa of choline and cytidine has been discussed, based on the differences in relative amount of radioactivity in individual broken-down products in the intestinal lumen and mucosa.It has been established that B vitamins exist in nature mostly in their coenzyme forms. Despite the general interest in the intestinal absorption of these vitamins and coenzyme forms subsequent to their recent clinical uses for therapeutic pur poses, our knowledge is very limited. Even the long dispute of whether vitamin Bl is absorbed after phosphorylation (1, 2), or passively without chemical changes (3), has not as yet been settled, although more recent data suggest active transport across the intestinal mucosa involving phosphorylation (4, 5).Coenzyme forms of B vitamins are relatively unstable in the gut. Flavine

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The author has already reported that 2-ketogulonic acid methylester (KGM) has an antiscorbutic action and, in the presence of the extract from plant and animal tissues, SH-compounds, barbituric acid derivatives etc., turn into a Vitamin C-like substance, which, in the author's opinion, is decided as ascorbic acid (AsA) (1-4). If so, what sort of mechanism is at work for the formation of Vitamin C from KGM ? Is the Vitamin C produced directly by enolisation and lactonisation from KGM which may take place? Or might it be assumed that Vitamin C is formed through some intermediary produced from KGM ? * Prof .: A. UETA, M. D.

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