An experimental study of hemolysis induced by onion (Allium cepa) poisoning in dogs

The mechanism of hemolysis induced by onion poisoning in dogs was studied. Six adult, clinically normal Pekingese dogs were fed cooked onions at 30 g/kg body weight/day for 2 days. Blood samples were collected on days 1, 3, 5, 8, 12, 18 and 24 after onion administration, and urine was collected the day after bleeding. Red blood cell counts, hemoglobin and hematocrit were decreased from day 1, and significantly so on day 5 ( P < 0.01), contrary to the results of white blood cell counts. So the plasma bilirubin levels and urobilinogen were increased on day 3 ( P < 0.01) and day 4 ( P < 0.01), respectively. The Heinz body counts were increased dramatically from day 1 ( P < 0.01), peaking on day 3 ( P < 0.01). Reticulocyte counts were increased from day 1 and the highest value was on day 8 ( P < 0.01). Besides anemia, the following erythrocyte parameters were altered: erythrocyte glucose‐6‐phosphate dehydrogenase was reduced from day 1 and reached the lowest value on day 5 ( P < 0.01); the reduced form of nicotinamide adenine dinucleotide phosphate was decreased on day 1 ( P < 0.01); reduced glutathione was decreased from day 1 ( P < 0.01) and the lowest value was on day 3 ( P < 0.01); glutathione‐peroxidase was increased on day 1, but decreased significantly on day 3 ( P < 0.01); hydrogen peroxide was increased on day 1 ( P < 0.01), then went down on days 3–12 (the undermost value on day 5, P < 0.01); catalase was risen dramatically on day 5 (the peak value, P < 0.01); malondialdehyde (MDA) was increased on days 1–8, ( P < 0.01), and reached the peak value on day 5 ( P < 0.01). Deformity of the erythrocyte membrane was decreased on days 1–12 and fluorescence polarization (ρ) and microviscosity (η) of the erythrocyte membrane were increased on days 1–12 ( P < 0.01). There were positive correlations between MDA and ρ as well as η, with correlation coefficients of 0.908 and 0.922, respectively ( P < 0.01), but there was a negative correlation between MDA and deformity index, with a correlation coefficient of −0.887 ( P < 0.05). This study confirmed that onion poisoning in dogs causes hemolytic anemia.