Evaluation of the cytotoxic and genotoxic effects by melamine and cyanuric acid co-exposure in human embryonic kidney 293 cells

The melamine and cyanuric acid (CA) complex has been suggested to cause the toxic effects observed in melamine-contaminated food or milk. However, the cytotoxic and genotoxic effects of co-exposure to melamine and CA are not fully clear. Therefore, the cytotoxic effects of melamine and CA were first examined by co‐exposure in human kidney 293 cells using the MTT assay. During a 24-h period for the three concentrations tested (0.5, 1, and 5 mg/mL), neither melamine nor CA alone showed significant toxic effects on 293 cells at 0.5 mg/mL, while higher concentrations led to decreased in cell viability. However, co-exposure to several combinations of melamine and CA [100:1, 10:1, 1:10, and 1:100 (v:v), at a final concentration of 0.5 mg/mL] did cause cytotoxicity with higher levels of CA leading to higher cytotoxicity. By contrast, while neither melamine nor CA alone induced phosphorylated-H2AX (γH2AX) foci formation, melamine and CA at a 100:1 ratio induced γH2AX foci 24 h post-treatment. The alkaline comet assay also revealed the presence of DNA damage following melamine and CA co-exposure. In vivo assay also revealed the presence of melamine-CA complex in the kidney. These data indicated that the cytotoxic and genotoxic effects of melamine and CA co-exposure differ from those of melamine or CA alone.

Synergistic effect of melamine in combination with cyanuric acid on urinary tract toxicity in rats / 동물의과학연구지

The present study investigated the urinary tract toxicity of melamine alone or in combination with cyanuric acid in rats. Male rats were orally administered melamine alone (800 mg/kg) or melamine plus cyanuric acid (50 mg/kg each) for 3 consecutive days. Although melamine treatment did not show any significant difference in body weight, kidney or urinary bladder weight, serum blood urea nitrogen (BUN) or creatinine levels, it caused a decrease in urinary pH and mild histopathological alterations in the kidney and urinary bladder. In contrast, co-administration of melamine and cyanuric acid induced a decrease in body weight, an increase in kidneys and urinary bladder weights, and an elevation in serum BUN and creatinine levels, which were not observed in animals treated with melamine alone. Histopathological examination showed that the incidence and severity of histopathological lesions in the kidney and urinary bladder were much higher than those in the melamine group. Urinalysis revealed an increase in urine occult blood, leukocytes and protein and a decrease in urinary pH. These results indicate that concomitant administration of cyanuric acid synergistically potentiated the urinary tract toxicity induced by melamine in rats. In this study, we first demonstrated the synergistic toxic effects of melamine in combination with cyanuric acid on urinary bladder and urinalysis in rats.

Increased Nephrotoxicity after Combined Administration of Melamine and Cyanuric Acid in Rats / 한국실험동물학회지

Renal toxicity by melamine in combination with cyanuric acid (1:1) was investigated. Male rats were orally administered melamine plus cyanuric acid (5, 50 or 400 mg/kg each) for 3 days. In contrast to a negligible effect by melamine alone (50 mg/kg, a no-observed-adverse-effect-level: NOAEL), co-administration with cyanuric acid markedly increased the concentrations of blood urea nitrogen and creatinine, as well as kidney weight. A high dose (400 mg/kg) of melamine plus cyanuric acid induced more severe kidney toxicity. The increased blood parameters for kidney toxicity and organ weight lasted longer than 4 days. Combined treatment with melamine and cyanuric acid (50-400 mg/kg each) resulted in many gold-brown crystals and toxic lesions in renal tubules, which were not observed in animals treated with melamine alone (50 mg/kg). These results indicate that only a 3-day exposure to melamine in combination with cyanuric acid causes severe renal damage, even at a NOAEL for melamine found in a 13-week toxicity study. Therefore, it is suggested that the tolerable daily intake or regulatory/management levels of melamine need to be re-considered for cases of co-exposure with cyanuric acid.

Study the toxicology damage of melamine(cyanuric acid) to rats kidney / 重庆医科大学学报

Objective: Study the toxicology damage of melamine(cyanuric acid) to rats' kidney.Methods: Divided the newborn rats and adult rats into high dose group of melamine(NM,M),low dose group of melamine(Nm,m),high dose group of cyanuric acid(NA,A),low dose group of cyanuric acid(Na,a),high dose group of melamine-cyanuric acid(NMA,MA),low dose group of melamine-cyanuric acid(Nma,ma) and normal control group(NN,N).The corresponding dose of melamine(cyanuric acid) was given by oral gavage and lasted two months.Rats were killed at 3 day,15 day and 60 day.The body weight and kidney weight were collected.Renal function was detected and the microscopic and ultra-microscopic renal histology structural changes were observed.Results: The body weight of NMA group and Nma group increased first,and then reduced.The body weight of MA group and ma group reduced gradually.The number of kidney crystal increased with the administration time extension.The electron microscope demonstrated that the tubules which contained stones microvilli reduced or disappeared,granulocyte infiltration and other inflammatory response.The kidney weight/body weight,urea nitrogen,creatinine,uric acid value increased in administration groups.Conclusion: Melamine(cyanuric acid) could produce insoluble crystals in rat kidney and lead to renal dysfunction.The toxicity of melamine(cyanuric acid) was greater in adult rats than in newborn.The number of melamine(cyanuric acid) crystals was positively correlated with dose and time.The toxicity of melamine was greater than cyanuric acid.Melamine(cyanuric acid) mixture toxicity was greater than the monomer.Melamine(cyanuric acid) toxicity had individual differences and brood diffenence.

Renal Toxicity Induced by Melamine Intake Single and Combined with Cyanuric Acid / 环境与健康杂志

Objective To explore the renal toxicity induced by melamine intake single and combined with cyanuric acid.Methods Thirty-six clean weanling male Wister rats were randomly divided into 3 groups,12 in each,treated with melamine and cyanuric acid through food for 28 consecutive days,group 1 treated with melamine at 25 mg/kg,group 2 treated with melamine (25 mg/kg) plus cyanuric acid (25 mg/kg),group 3 is control,fed on normal pet food.After 4 weeks of treatment,the rats were sacrificed and blood indicators,histopathological examination of kidney were conducted.Renal tissues from the affected rats were analyzed using high-performance liquid chromatography and mass spectrometry.Kidney X-ray diffraction was performed to determine the existence of crystals.Results In group 1 and 2,polyuria,hypokinesia and weight loss (P