Tissue distribution and prediction of total body folate of rats.

To clarify relationships between dietary folic acid intake, blood levels and body stores of folate, rats were fed an amino acid-based diet supplemented with 0, 0.125, 0.5, 1, 2 or 4 mg folic acid/kg diet for 25 d. Folate concentrations of carcass, liver, gastrointestinal (GI) tract, kidney, spleen, testes, heart and lung from rats fed the folate-free diet were 0.06 +/- 0.01, 0.73 +/- 0.08, 0.05 +/- 0.01, 0.39 +/- 0.01, 0.05 +/- 0.01, 0.17 +/- 0.01, 0.02 +/- 0.01 and 0.02 +/- 0.01 micrograms/g, respectively. Serum and erythrocyte concentrations and total body stores were 0.88 +/- 0.16 ng/mL, 0.30 +/- 0.01 micrograms/mL and 13.9 +/- 0.7 micrograms, respectively. Body folate distribution was carcass, 55.6 +/- 1.4%; liver, 26.0 +/- 1.9%; erythrocytes, 7.7 +/- 0.4%; kidney, 4.8 +/- 0.2%; GI tract, 3.0 +/- 0.2%; and testes, 2.5 +/- 0.2%. Carcass content dropped to 38% whereas liver content increased to 44% in rats fed the highest dietary level. Tissue concentrations were correlated with one another and with dietary folate levels. Under these experimental conditions total body folate could be predicted from serum folate, but the general applicability of this relationship requires further study.