Methemoglobin Reductase Deficiency in a Dog

SUMMARY In a case of canine methemoglobinemia the only significant clinical findings were brownish mucous membranes and dark, brownish blood. Chemical analysis indicated a methemoglobin concentration that was approximately 30% of the total hemoglobin. There was no basis in the history or clinical findings to suggest a drug-induced methemoglobinemia. Electrophoretically, the methemoglobin migrated identically to that prepared from normal canine hemoglobin by treatment with sodium nitrite, indicating that there was no hemoglobinopathy. Enzymatic analysis revealed nicotinamideadenine dinucleotide (nadh)-methemoglobin reductase activity of 0.50 i.u./Gm. Hb., which was 23.6% of the mean value (2.12 i.u./Gm. Hb.) for 10 control dogs. The methemoglobinemia was attributed to this decrease in nadh-methemoglobin reductase activity.