The Clinical and Experimental Studies on the Metabolism of Folic Acid Using Tritiated Folic Acid

II. The Experimental Studies on the Absorption Site and Mechanism of Tritiate Folic Acid in Rats

Abstract

1. The site and mechanism of folic acid (FA) absorption were studied in the rat, using ³H-FA.
2. After intragastric administration of 40μg of ³H-FA per kg of body weight, 79.3 per cent of the administered dose was absorbed from the upper gastrointestinal tract in 6 hours.
3. From the jejunal loop, 91.7 per cent of the injected dose was absorbed in 6 hours, and the absorption from the ileum was about 50 per cent of that from the jejunum.
4. With the increase of administered doses, the rate of absorption was decreased, while the absolute amount of the absorbed FA increased almost linearly.
5. The absorption of FA was not affected by the following conditions: simultaneous administration of Amethopterin or dinitrophenol, pretreatment with Amethopterin or FA, and deficiency of FA.
6. The site and mechanism of FA absorption were discussed and a passive transport for FA was suggested.