Melamine is an important and widely used organic
industrial chemical. Recently, clinical findings of renal failures and renal
calculi in infants have been associated with the ingestion of melamine-contaminated infant formula. Melamine is also present in plastic materials which are widely
used in the world. The toxicity of melamine caught the attention of physicians
as a result of a recent spate of renal injury after exposure to
melamine-tainted milk. Melamine is an organic nitrogenous compound used in the
production of plastics, dyes, fertilizers, and fabrics. In the current
incident, melamine was added to milk to elevate false assay results for
protein content. A variety of toxic effects from melamine, include nephrolithiasis, chronic kidney inflammation, and bladder carcinoma.
The mechanism of melamine nephrotoxicity is still unknown,
but clues are available from animal studies. Melamine is rapidly excreted in
the urine (90% of the administered dose in 24 h), but
melamine can precipitate in distal renal tubules. Histopathologic specimens from affected cats and
dogs from the 2004 and 2007 outbreaks show characteristic intratubular green
radial crystals and crystalluria. The morphology and histochemical staining pattern are distinct from
calcium oxalate or calcium phosphate crystals. Some affected animals suffered from acute kidney injury (AKI), whereas others
developed chronic kidney disease (CKD). Melamine-associated AKI in animals was
characterized by necrosis of distal tubular cells and mild inflammation.
Chronic toxicity showed larger crystals, interstitial inflammation, and
fibrosis.
Melamine and related amine analogs have natriuretic properties in dogs at
a dose of 125mg/kg, and thus, may exacerbate AKI by leading to pre-renal
azotemia in susceptible animals or individuals. The nitrogen content of melamine is unlikely to artificially increase the
blood urea nitrogen (and thus feign AKI) because, in autopsy studies, detection
of melamine in diseased renal tissue occurred in the absence of melamine
metabolites.
Currently, various medicinal plant extracts and compounds are tested for anti-melamine-induced renal calculi. Moreover, the molecular mechanisms of the treatment will also be investigated using different molecular techniques.
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