The objective of this study was to investigate the possible target cells during acute renal toxicity of melamine and cyanuric acid (MCA) mixture crystals in vivo. Rats were provided with a lethal dose of MCA (1:1; 400 mg/kg) and observed after 0.5, 1, 3, 12, 24, and 48-h intervals.
MCA caused degeneration/necrosis in the proximal tubules starting at 12 h and increased at 24 and 48 h. A small number of yellow-green crystals were observed in the dilated distal renal tubules at 48 h post-treatment. Ultrastructurally, pyknosis, mitochondrial vesicles, and cellular swelling were found in the proximal tubular cells at 0.5 h. Small needle-like crystals in the cytoplasm and large crystals in the lumen of tubules indicated physical damage to the renal cells.
These results clearly reveal that in the MCA-induced renal toxicity model, crystals are distributed to both the proximal and distal tubules in rats. The proximal tubular cells may be initially injured and subsequently block the distal tubules with MCA crystals during early acute intoxication.