Adverse effects of herbicide MCPA on dogs in a 90 day toxicological study.

OBJECTIVES: This study was performed to investigate the toxicity of the herbicide MCPA after repeated treatment according to OECD No 409.

METHODS: The herbicide MCPA was administrated to dogs of both sexes in daily doses: 0, 1, 5 and 15 mg/kg per os during 90 days. Clinical observations were recorded, opthalmoscopic, haematological, clinical chemistry parameters were investigated. The morphological changes were examined using pathological and histological techniques.

RESULTS: An increase in the activity of the enzyme ALT and of urea concentration was observed in the middle- and high-dose groups. ALP and creatinine were decreased in dogs of all dose groups. After 60 days of MCPA administration, the concentration of glucose decreased in the high-dose group. The relative weight of both testes was decreased in the males from the high-dose group in comparison to controls. The decrease in testes weight was associated with focal testicular atrophy and loss of spermatogenic cells in the lobuli of testes. Focal hepatocellular necrosis, inflammatory changes and mononuclear nodules were observed in the liver, predominantly in males of the high-dose group.

CONCLUSIONS: Administration of MCPA did not cause mortality and had no adverse effects on hematological parameters of animals. The results of the study showed that MCPA treatment caused inflammatory lesions in the liver, moderate damage of the kidney, and had focal adverse effect on the development of spermiogenesis. The changes were reversible.