Mechanism of crystals’formation induced by melamine in kidney and the relationship between crystals and kidney injury

Objective To research the mechanism of renal injury induced by melamine in rats.Methods The Wistar rats of clean grade were randomly divided into the exposure groups and the control group,the kidney samples were collected after different exposure times and tested by visual inspection,pathological examination and serum biochemical detection.The crystals formed in kidney were qualitatively and quantitatively analyzed by Lc-mc and X-ray diffraction(XRD).According to the reaction heat of melamine and cyanuric in vitro,the relationship of crystals formation to tubular injury was analyzed.Results After exposure,the serum creatinine(CRE),blood urea nitrogen(BUN),triglyceride(TG) were increased.The renal appearance showed abnormal changes and the renal thick sections were observed under dissection microscope,it showed that diffuse distribution of sediment-like foreign bodies’shadow.Pathological examination showed crystals in renal tubules and the epithelial secondary injury of renal tubules.The melamine concentration was 147.3 μg/g and the cyanuric acid concentration was 122.6 μg/g in renal tissue tested by Lc-mc.The renal crystals were confirmed to be crystal combination of melamine and cyanuric acid by X-ray diffraction.The results of melamine and cyanuric acid reaction heat test showed that 94KJ/mol was produced during forming crystals.Conclusion The crystals can formed in tubules after oral exposure.Crystals blocked the renal tubular,which led to re-absorption dysfunction;and a large number of crystals caused severe kidney ischemia and hypoxia;the instantaneous reaction heat of melamine-cyanuric acid can lead to the renal tubular degeneration.The combined action of these three lead to renal injury.