Methotrexate effects on folate status and the deoxyuridine suppression test in rats

Abstract

Methotrexate (MTX) was administered to rats to produce marked folate deficiency to develop an experimental model for studying folate coenzyme abnormalities. Male Sprague-Dawley rats were fed control and experimental, folate-deficient diets, with or without MTX (0.1 mg/100 g body wt) i.p. every other day for 2 wk. The MTX-treated rats developed severe folate deficiency signs, including diarrhea and impaired growth. Cytological features of megaloblastic anemia seen in peripheral blood in the folate-deficient group (FD)+MTX rats were RBC macroovalocytosis, anisocytosis and elevated neutrophil lobe counts, in comparison to both MTX-untreated FD and control rats. Urinary formiminoglutamic acid (FIGLU) excretion was elevated and RBC folate depressed in these FD+MTX rats. The dU suppression test in isolated lymphocyte cultures showed abnormal and higher [ 3H]thymidine uptake by DNA in both MTX-treated and untreated FD groups at 11 wk, but only in FD-MTX at 5 wk; this was associated with lower plasma folate values. Thus, these results indicate that MTX-treated rats have a more severe folate deficiency than that produced by a folate-deficient diet alone.