Study On Melamine Toxicity

The toxicity of melamine and the safety of the food attracts the public attention as a result of renal injury after exposure to melamine-contaminated milk in September 2008. This study focused on evaluating melamine's acute toxicity, subchronic toxcity, special toxicity and the effect on cell apoptosis completely, aimed at providing reference for people who may exposure to melamine, the treatment of poisoning and the toxic mechanisms. The study includes 4 parts:1. The acute toxicity and accumulative toxicity of melamine in miceTo observe the acute toxicity and the accumulative toxicity of mice exposed to melamine by the modified Korbor method and fixed dose method. The results showed that the toxic symptoms including activity decreased, respiratory distress and anorexia; Kidney, lung, liver and spleen of dead mice showed gross lesions and histopathological changes. The LD50 of melamine to mice was 2958.69 mg/kg, with 95% confidence interval of 2187.00～3981.07 mg/kg. The results of accumulative toxicity test showed that the accumulative coefficient K was 4. In accordance with the acute toxic standard of food safety, melamine possesses low toxicity and moderate accumulative toxicity in mice.2. Subchronic toxicity study of melamineThis part includes 30-d subchronic toxicity study on mice and 90-d subchronic toxicity on rats.Kunming mice were randomly divided into 4 groups,20 mice per group:High melamine (49.3 mg/kg.bw/d), middle melamine (19.7 mg/kg.bw/d), low melamine (3.0 mg/kg.bw/d), control group, the experimental period was for 30 days. The results indicated that the body weight gains of all the treated animals were slow, food utilization ratios were significantly reduce (p<0.01); LYM, monocyte levels significantly increased in the high dose groups compared with control (p<0.05); ALT, AST, BUN, Cr and UA levels significantly increased, Ca and P levels significantly decreased in the high and middle dose groups compared with control (p<0.05); Liver and kidney index significantly increased in the high groups (p<0.05), spleen index significantly decreased in the high and middle dose groups (p<0.05); Histopathological examinations indicated that significant lesions in the lung, liver, spleen, kidney and bladder occurred in the high and middle dose groups. These results suggested that melamine could influence growth of mice, and cause lung, liver, kidney and spleen injury in subchronic toxicity.Rats were randomly divided into 4 groups,20 rats per group:high melamine (16.44 mg/kg.bw/d), middle melamine (6.57 mg/kg.bw/d), low melamine (1 mg/kg.bw/d), control group, the experimental period was for 90 days. The results indicated that the body weight gains of all the treated animals were slow, food utilization ratios were significantly reduced (p<0.01); There were no significant difference about the hematological parameters in the dose group compared with control. ALT, AST, BUN, Cr and UA levels significantly increased, Ca and P levels significantly decreased in the high and middle dose groups compared with control (p<0.05); Histopathological examinations indicated that significant lesions in the lung, liver, spleen, kidney and bladder occurred in the high and middle dose groups. These results suggested that melamine could influence growth of rats, and cause lung, liver, kidney and spleen injury in 90-d subchronic toxicity.3. Special toxicity of melamineThis part includes the effects of melamine to micronucleus of NIH mice's bonemanow cell, sperm abnormalities, the embryonic and teratogenic toxicities.The effects of melamine to micronucleus of NIH mice's bonemanow cell was designed to 3 experimental groups:High melamine (1479.35 mg/kg.bw), middle melamine (591.74mg/kg.bw), low melamine (295.87 mg/kg.bw), positive control group cyclophosphamide (60 mg/kg.bw) and negtive control group (distilled water), which consisted of 10 mice. The test was carried out by twice exposure method at 24 h interval. The results indicated that the micronucleus of NIH mice's bone manow cell ratios of the positive were significantly compared with the negtive group, the melamine treated group's micronucleus of NIH mice's bone manow cell ratios were not significantly compared with the negtive group. There were no effects of melamine to micronucleus of NIH mice's bone manow cell at these dosages.The test of sperm abnormalities was designed to 3 experimental groups include the high dose group (1479.35 mg/kg.bw), the middle dose group (591.74 mg/kg.bw) and the low dose group (295.87 mg/kg.bw), positive control group (60 mg/kg.bw) and negtive control group (distilled water). Dose the treated and the negtive group by oral administration for 5 times. The mice were sacrificed to examine the sperm after 35 days of the first dosage. The results indicated that the sperm abnormalities rate of the positive control group was significant increase when compared with the negtive control group (P<0.01). The sperm abnormalities rate of the middle and the high treated group was significant increase when compared with the negtive control group (P<0.05). These results suggested that melamine could influence the sperm abnormalities of mice.The test of the embryonic and teratogenic toxicities mice were radomly divided into 5 groups with 20 mice in each, include the high dose group (98.2 mg/kg.bw/d), the middle dose group (39.4 mg/kg.bw/d) and the low dose group (19.7 mg/kg.bw/d), positive control group (60 mg/kg.bw/d) and negtive control group (distilled water). The result showed that melamine didn't produce significant efffects on health, behavior, weight gain and reproductive parameters of pregnant mice and fetal growth, and didn't induce any teratogenic effect on the appearance, bones and bowels of the fetuses. Melamine has no embryonic and teratogenic toxicity when used 98.2 mg/kg.bw/d-19.7 mg/kg.bw/d.The effect of melamine on the apoptosis to different tissue cellTo study the effect of melamine on the apoptosis of kidney cell, liver cell, spleen cell and lung cell in Kunming mice which include the high melamine (1479 mg/kg.bw), middle melamine (739 mg/kg.bw), low melamine (370 mg/kg.bw), control group (distilled water), the experiment was conducted by the methods of flow cytometry (FCM). The results showed that the percentage of renal cell apoptosis and lung cell apoptosis was significant increased in melamine treated groups when compared with that of control group (p<0.05). It is concluded that melamine induced renal cell apoptosis and lung apoptosis in mice when used 1479 mg/kg.bw-370 mg/kg.bw.