The molecular pathology of chronic nitrate intoxication in domestic animals: a hypothesis.

The controversial situation of chronic low level nitrate intoxication may involve oxidation of important iron-containing enzymes, much like oxidation of hemoglobin (Fe++) iron to methomoglobin (Fe+++). This oxication causes enzyme inhibition and unlike hemoglobin, which has the methemoglobin reduction system, these enzymes remain in the oxidized state, resulting in the clinical signs and conditions described. This condition may be diagnosed more accurately by measuring erythrocyte catalase activity in addition to blood or dietary levels of nitrate.