Effect of urinary pH upon the renal toxicity of melamine and cyanuric acid

In 2007, dietary exposure to “scrap melamine’ resulted in the death of a large number of cats and dogs, which was attributed to the formation of melamine cyanurate crystals in their kidneys. In this study, we investigated if changes in urinary pH could diminish the renal toxicity associated with exposure to combinations of melamine and cyanuric acid. Female Sprague-Dawley rats were treated for three days with suspensions of melamine and cyanuric acid at doses that were expected to induce renal toxicity. Dosing was then discontinued and the rats were treated for seven days with drinking water solutions (i.e., ammonium chloride and sodium bicarbonate) that would alter urinary pH. The urinary pH of rats administered ammonium chloride drinking water decreased from pH 6.0–6.2 to pH 5.1–5.2. This was accompanied by a decrease in the incidence of melamine cyanurate crystals in the kidneys and a decrease in the incidence of renal lesions. These data suggest that acidification of urine may help overcome the renal toxicities associated with the formation of melamine cyanurate crystals in the kidney.