Biliary excretion and microfloral transformation of major conjugated metabolites of 2,4-dinitrotoluene and 2,6-dinitrotoluene in the male Wistar rat

Abstract

1. Major biliary conjugates of the male Wistar rat dosed orally with 2,4-dinitrotoluene (2,4-DNT) or 2,6-dinitrotoluene(2,6-DNT) were examined by hplc using potassium 2,4- dinitrobenzyl glucuronide (potassium 2,4-DNB- G), potassium 2,6-dinitrobenzyl glucuronide (potassium 2,6-DNB- G), pyridinium 2,4-dinitrobenzyl sulphate (pyridinium 2,4- DNB- S) and pyridinium2,6-dinitrobenzylsulphate (pyridinium2,6-DNB- S) as authentic compounds. Other metabolites were also examined by hplc. In addition, metabolites formed by incubation of potassium 2,4-DNB- G and potassium 2,6-DNB- G with rat intestinal microflora under nitrogen were examined by hplc. 2. Conjugates detected directly from bile following administration of 2,4-DNT and 2,6-DNT were 2,4-DNB- G and 2,6-DNB- G, which accounted for 35 0 and 51 5 % of the administered dose respectively. No peaks corresponding to pyridinium 2,4-DNB- S and pyridinium 2,6-DNB- S were detected in bile samples. 3. 2-Amino- 4-nitrotoluene,4-amino- 2-nitrotoluene,2,4-diaminotolueneand 4-acetylamino- 2-nitrobenzoic acid (0 02-0 12 % of the dose excreted in 24 h), in addition to the known metabolites 2,4-dinitrobenzyl alcohol (2,4-DNB), 2,4-dinitrobenzalde hyde and 2,4-dinitrobenzoic acid (0 09-0 14 %), were detected in ether extracts of bile of rat given 2,4-DNT. 2,6-Dinitrobenzylalcohol (2,6-DNB), 2-amino- 6-nitrotolueneand 2,6-dinitrobenzaldehyde(0 02-0 03 %), which are known metabolites, were detected in ether extracts of bile from rat given 2,6-DNT. 4. Potassium 2,4-DNB- G was transformed by the anaerobic incubationof rat intestinal microflora into 2,4-DNB, 4-amino- 2-nitrobenzyl alcohol and 2-amino- 4-nitrobenzyl alcohol. Potassium 2,6-DNB- G was transformed into 2,6-DNB and 2-amino- 6-nitrobenzyl alcohol by the anaerobic incubation. Time-course studies showed that 2,4-DNB, 4-amino- 2-nitrobenzyl alcohol, 2-amino- 4-nitrobenzyl alcohol and 2,6-DNB, 2-amino- 6- nitrobenzyl alcohol peaked at 30, 75, 120 and 10, 50 min respectively. 5. These results, together with previous findings, show that 2,4-dinitrobenzalde hyde and 2,6-dinitrobenzalde hyde, which are potent mutagens, are formed either by the hepatic metabolism of 2,4-DNB and 2,6-DNB formed by the intestinal metabolism of 2,4-DNBG and 2,6-DNB- G excreted in bile or by the direct hepatic metabolism of 2,4-DNT and 2,6-DNT.