Use of the deoxyuridine suppression test to evaluate localized folate deficiency in rat colonic epithelium

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Abstract
In this study the deoxyuridine suppression test (dUST) was performed on isolated rat colonocytes to establish its value as an indicator of folate status in the colonic epithelium. [3H]thymidine incorporation into DNA was suppressed < 90% by deoxyuridine (dU) concentrations < 2.5 µmol/L. Preincubation of cells with 5-fluorouracil (1–100 µmol/L) but not methotrexate (10–100 µmol) resulted in a significant decrease in the degree of suppression. The dUST performed on colonocytes from folate-deficient animals displayed less suppression than on colonocytes from folate-replete animals (P < 0.05). The abnormal degree of suppression was corrected by adding 100 µmol folinic acid/L. There was a negative correlation between the degree of suppression and the folate concentration of the colonic epithelium (P < 0.001). These data indicate that the dUST is useful for detecting folate deficiency in the colonic epithelium and may therefore be valuable in assessing a deficiency state localized to that epithelium.