The recent tainting events of milk and pet foods with melamine and melamine-related compounds (MRCs), in attempts to elevate the total nitrogen content, have led to many cases of acute renal failure in infants and domestic pets. In this study, we employed matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry-based imaging mass spectrometry (IMS) technique to visualize the distribution of melamine in renal tissue. For rats orally administered with melamine alone, the protonated melamine ion at m/z 127 was detected only in the papilla. No melamine signal was detected in the kidney of rats receiving cyanuric acid alone. Melamine was accumulated in kidney only when the rats received high dose of melamine (100 mg day−1) together with cyanuric acid for 3 days. Under such regimen, the molecular signal was visible in both cortex and medulla, with an accumulation in renal papilla. Our IMS results for rat renal tissue are consistent with previous reports and histological observations. Nonetheless, there was no difference between the lipid distributions on the renal tissues of the control rats and those administered with melamine/cyanuric acid.
