Research On Long-term Damage To Animal Urinary System Caused By Intake Of Melamine

Objective:To explore the long-term damage to animal pig urinary system caused by melamine and relevant injury reversibility.Methods:18 experimental pigs were randomly divided into three groups,6 pigs for each group:group A (low concentration of melamine), group B (high concentration of melamine) and the control group (without adding melamine into feed). Experiment I: Experimental pigs were separately fed for 5 months by dividing them into different groups based on daily food and water intake. The general growth situations were recorded. Serum creatinine and urea nitrogen were measured. Unilateral kidneys were randomly sampled for pathological examination. Experiment Ⅱ:Intake of feed containing melamine was stopped in group A and group B. And pigs in both groups were fed based on calculated daily intake under normal conditions. The general growth situations of pigs in the tree groups were observed and blood biochemical levels (creatinine and urea nitrogen) were detected monthly. After stopping intake of melamine to practice normal feeding for 12 months, the rest kidneys were taken to make bladder pathological sections. Statistical processing was conducted by using SPSS 18.0 software.Results:1.Observation of the body weights of experimental pigsThe body weights of experimental pigs in control group, group A and group B were increased after feeding for 5 months and stopping intake of melamine for 12 months respectively. The increase of body weight in group B was much slower than those in other groups, showing statistically significant differences.2. Observation of the creatinine levels of experimental pigsThe cretinine levels of experimental pigs in the control group and group A had no obvious changes after feeding for 5 months and stopping intake of melamine for 12 months, while that in group B declined, showing statistically significant differences.3. The urea nitorgen levels of experimental pigs in the control group and group A had no obvious changes after feeding for 5 months and stopping intake of melamine for 12 months, while that in group B declined, showing statistically significant differences.4. Renal pathological changesAfter stopping intake of melamine for 12 months, the control group had no abnormal change. Group A:Renal cortex can be noted in the pig renal specimens in this group. There was no formation of medullary crystals. The glomerulus was morphologically normal and no obvious renal intersititum edama. A small amount of exfoliation of renal tubular epithelia cells was observed. Mucosal edema was improved. No exfoliation of epithelial cells and mucosal edema were found. The bladder mucosa was complete and no stone was noted. Group B:Glomerulus could be noted. There were renal tubular epithelia cell edema and mild interstitial congestion. No formation of crystal stones was noted in renal cortex, medullar and calyx. No formation of crystal stones was noted in renal tubules and glomeruli. There was mild renal tubular edema and no mucous exfoliation. The renal pelvis mucosa was complete and no mucous exfoliation. The bladder mucosa was complete and no stone was notedConclusion:1. Long term intake of high dose of melamine has definite damage to renal function, and in severe cases, it even cause renal failure and finally lead to death.2. After stopping the intake of melamine for one year, pathological injury in the high concentration group is recovered and no stone is formed, suggesting the irreversible recovery of renal functions.