Oral administration of potassium bromate, a major water disinfection by-product, induces oxidative stress and impairs the antioxidant power of rat blood

Potassium bromate (KBrO₃) is a widely used food additive, a water disinfection by-product and a known nephrotoxic agent. The effect of KBrO₃ on rat blood, especially on the anti-oxidant defense system, was studied in this work. Animals were given a single oral dose of KBrO₃ (100 mg/kg body weight) and sacrificed 12, 24, 48, 96 and 168 h after this treatment. Blood was collected from the animals and separated into plasma and erythrocytes. KBrO₃ administration resulted in increased lipid peroxidation, protein oxidation, hydrogen peroxide levels and decreased the reduced glutathione content indicating the induction of oxidative stress in blood. Methemoglobin levels and methemoglobin reductase activity were significantly increased while the total anti-oxidant power was greatly reduced upon KBrO₃ treatment. Nitric oxide levels were enhanced while vitamin C concentration decreased in KBrO₃ treated animals. The activities of major anti-oxidant enzymes were also altered upon KBrO₃ treatment. The maximum changes in all these parameters were 48 h after the administration of KBrO₃ and then recovery took place. These results show for the first time that KBrO₃ induces oxidative stress in blood and impairs the anti-oxidant defense system. Thus impairment in the anti-oxidant power and alterations in the activities of major anti-oxidant enzymes may play an important role in mediating the toxic effects of KBrO₃ in the rat blood. The study of such biochemical events in blood will help elucidate the molecular mechanism of action of KBrO₃ and also for devising methods to overcome its toxic effects.     

Nitrate/nitrite poisoning in dairy cattle associated with consumption of forages irrigated with municipally treated wastewater

Twenty-three cases of nitrate poisoning were diagnosed in a dairy herd due to consumption of green grass, mainly alfalfa, which was irrigated with a municipally treated wastewater. Five cows were found dead and seven fetuses were aborted. Methemoglobin (MtHb) in blood reached 41.6 ± 7.5%, while hemoglobin concentration was low: 6.9 gm dL^–1. Nitrite in plasma was 1.6 ± 0.4 mmol; the levels of nitrate in suspected grass and water were 1.48 × 10³ ppm and 1.7 × 10³ ppm, respectively. The clinical picture included difficulty in breathing, shivering and brown discoloration of the mucous membranes of the vulva, vagina, and conjunctiva. The postmortem findings included dark brown carcasses with dark, nonclotted blood in the dilated vessels. Cardiac hemorrhages, pulmonary and rumen congestion, edema and hyperemia of the mucous membranes of the abomasums and small intestine were noticed in all examined animals. The postmortem examination of aborted fetuses revealed severe ascites and hydrothorax. Affected animals responded well to the treatment with methylene blue. After one week of treatment MtHb and nitrite in plasma were significantly reduced to their minimal levels (10.5% and 0.5 mmol), respectively. One week later, green-feed and water had no evidence of nitrate. A definitive diagnosis was made based on the clinical picture, postmortem findings, high MtHb level in blood, quantitative nitrite analysis of plasma and nitrate analysis of suspected green-grass and response to methylene blue treatment.