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

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.