Ruminal metabolism of DNOC and DNBP

Abstract

The metabolism of DNOG and DNBP in rumen fluid was examined in vitro after elaboration of analytical methods for quantitative determination of dinitrophenols, their 6-amino derivative and diamino-phenols. It was shown that, under anaerobic conditions, the dinitrophenols were rapidly converted into 6-amino derivatives, which successively were reduced to diamino compounds. Reduction did not take place in heat-sterilized rumen specimens, and the metabolism was inhibited by high initial concentrations of the dinitro compounds in the rumen fluid (1—4 × 10⁻³M).

In vivo experiments were performed for determination of the concentrations of the dinitrophenols and their metabolites in rumen fluid and blood plasma in a cow. Ruminai metabolism was rapid like in vitro, and the parent compounds were reduced in 10—30 min. The 6-amino derivatives persisted in the rumen fluid for 1 nr., and thereafter only diaminophenols could be detected for another 8—10 hrs. At least 95 % of the absorbed DNOG or DNBP were bound to plasma proteins. 6-amino-4-nitro-o-cresol w^τas found in plasma exclusively in conjugated form, while 6-amino-4-nitro-sec.-butylphenol was free. The diamino compounds were not demonstrated in blood plasma.

Severe methaemoglobinaemia and haemolysis were seen after administration of DNBP. The difference in toxicity for ruminants between the two dinitrophenols is discussed on the basis of the observations reported pointing at the unconjugated 6-amino-4-nitro-sec-butylphenol as a potent inducer of methaemoglobinaemia.