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

I. Absorption Tests of Tritiated Folic Acid in Man

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1. The absorption tests of tritiated folic acid (³H-FA) and ⁶⁰Co-cyanocobalamin (⁶⁰Co-B₁₂) were carried out in normal subjects and patients with gastrointestinal or hematological diseases.
2. An oral dose of 40μg ³H-FA per kg of body weight was given 30 minutes after an injection of 15mg of non-radioactive FA. The urinary excretion of ³H-FA was estimated in following 24 hours. In some cases the fecal excretion of ³H-FA was measured for successive four days.
3. The urinary excretion of ³H-FA in eleven normal subjects ranged from 37.6 to 57.9 per cent of the oral dose, with a mean of 48.4 per cent and a standard deviation of 7.4 per cent. The fecal excretion ranged from 1.5 to 7.5 per cent of the dose with a mean of 3.5 per cent and a standard deviation of 3.5 per cent.
4. In some cases of gastrectomy, defective FA absorption was observed.
5. Decreased urinary excretion was found in patients with blind loop syndrome and also in some case of ileocolostomy.
6. Urinary excretion of ³H-FA was diminished in some cases of hematological disorders, such as pernicious anemia and leukemia.
7. The causes of defective FA absorption were discussed in each case.