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

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Abstract
The absorption of tritiated folic acid (3H-FA) and 60Co-cyanocobalamin (60Co-B12) was studied in normal subjects and patients with gastrointestinal or hematological diseases. An oral dose of 40 [mu]g 3H-FA per kg of body weight was given 30 min. after an injection of 15 mg 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. The urinary excretion of 3H-FA in 11 normal subjects ranged from 37.6 to 57.9% of the oral dose, with a mean of 48.4% and a standard deviation of 7.4%. The fecal excretion ranged from 1.5 to 7.5% of the dose with a mean of 3.5% and a standard deviation of 3.5%. In some cases of gastrectomy, defective FA absorption was observed. Decreased urinary excretion was found in patients with blind loop syndrome and also in some cases of ileocolostomy. Urinary excretion of 3H-FA was diminished in some cases of hematological disorders, such as pernicious anemia and leukemia. The causes of defective FA absorption were discussed in each case.