Folate Deficiency in Malnutrition, Malabsorption, and During Phenytoin Treatment Diagnosed by Determination of Serine Synthesis in Lymphocytes

Abstract A new method for the detection of folate deficiency by measuring the rate of incorporation of ¹⁴C-formate into serine in isolated lymphocytes has been applied to a group of 24 control subjects and 23 patients. 5 of the patients suffered from malnutrition, 14 had malabsorption and 4 were under treatment with phenytoin.
In 17 of these patients, functional folate deficiency was diagnosed by a decreased rate of serine synthesis in the lymphocytes. 11 cases of folate deficiency were found by measuring the folate concentration of erythrocytes by the L. casei method. The lymphocyte method failed in only one case out of 18.
In the 24 control subjects the average incorporation of ¹⁴C-formate into serine per 10⁹ lymphocytes per 4 h was 9.2 ± 0.4% (range 6.3–14.3 %) of added activity. For 16 patients with functional folate deficiency, the corresponding value was 4.1 ± 0.3% (range 1.0–5.9%). The folate activities of lymphocytes from 12 patients before and after 4 weeks of oral treatment with 15 mg folic acid daily were 3.4±0.3 and 7.5±1.0% respectively. The lymphocytes responded within 4 weeks to deprivation of or treatment with folic acid.
The ¹⁴C-formate incorporation into methionine, RNA sad protein showed the same pattern as the incorporation into serine.