The Experimental Investigation Of The Kidney Damages Caused By Melamine In Canine

Melamine, non food additive, is widely used in industry, which should not be consumed. It is illegal to mix melamine into the food of people and pets in order to boost the apparent protein level, this may induce poisoning of both people and pets. Several researches have proved that melamine has low toxicity. Melamine ingested in small doses is not life threatening, but ingested in large doses for long time may cause stones and illness. This paper aimed to observe the renal injury of the canine after continuous oral administration of certain melamine dosage. The observations included the changes in the blood routine indexes, the biochemical criterions and the ultrasound images during the feeding period. At the end of the feeding regimen, the kidney injury was proven by detecting the relative expression of OPN gene and CLU gene, the change of antioxidant enzyme activity and microstructure of kidney tissue.8 healthy canines were divided into two groups,3 canines in the control group and 5 canines in the experimental group. Before feeding, all canines were given a medical check up to measure their health status. Canines received oral administrations of melamine at a dose of 600 mg/kg body weight once daily over a period of 75 days. Blood was collected for blood routine test and biochemical tests and urine collections were centrifuged to observe the urinary sediment every 6 days. At the later stage of the feeding, all the canines received ultrasound examination to observe the kidney structure. The left kidney was removed surgically. The kidney tissue was used for analyzing microstructure, measuring the activity of antioxidant enzyme and performing real-time PCR. The results are as followed:(1) Exposure to melamine for 75 days changed the blood routine indexes and the biochemical criterions gradually. The total white blood cell counts and the total neutrophile granulocyte increased slightly. The ALT and AST levels began to rise significantly on the 62nd day (P< 0.05). The BUN and CREA levels continued to rise throughout the feeding. The exposure of melamine causes much of white precipitate, which is melamine crystals, in urine of dogs. The melamine crystals have many kind of shapes under the microscope. The ultrasonic images of the kidney showed the existence of the renal calculi.(2) The exposure of melamine for 75 days increased the relative expression of OPN gene and CLU gene of the kidney cortical tissue in the experimental group compare to control group, (P> 0.05). The relative expression of OPN gene of medullary kidney tissue increased significantly in the experimental group, (P< 0.05); and the relative expression of CLU gene of medullary kidney tissue increased extremely significantly in the experimental group, (P< 0.01).(3) The histopathology of kidney tissue indicated that the glomeruli and the renal tubular had both been damaged. Part of renal tubular was dilated, half of which had protein cast, half showing renal tubular atrophy. The renal interstitium had a hyperplasia of fibrotic tissue. Part of the glomerulis was infiltrated with cells which caused swelled resulting in the stenos or disappearance of renal capsules. The capillaries of the glomeruli disappeared or had expanded with visible protein deposits.(4) The exposure of melamine for 75 days led to a significant decline of the GSH-Px and SOD (P< 0.05); and a significant increase in MDA levels in the renal medulla of the experimental group compared to the control group (P< 0.05).These results suggest that oral administration of melamine to canines at a dose of 600 mg/kg body weight once a day over a period of 75 days will lead to renal calculi, urinary sediment, decline of antioxidant abilities and the damage of kidney tissue.