The effect of exogenous melamine on rat hippocampal neurons.

Rat hippocampal neurons in culture medium were exposed to different concentrations of melamine. By examining the morphology of cells detected with acridine orange staining, different changes of fluorescences of Ca2+ observed with Fluo3, and caspase-3 activity assayed with optical density by enzyme linked immunosorbent assay kit, we found the effect of melamine on hippocampal neurons. Pathologic changes happened in hippocampal neurons, and there seemed to be insoluble metabolites in most of the cells with 312 mu g/mL melamine stimulated for 12 hours. Then, we tested the Ca2+ fluorescences of the cells above. The free intracellular Ca2+ concentrations were measured using the fluorescent dye Fluo3. The average fluorescence of Ca2+ in hippocampal neurons stimulated by 312 mu g/mL melamine (55.43 +/- 3.54) was higher than the normal ones (6.94 +/- 0.14). Besides, caspase-3 activity of hippocampal neurons after being challenged with melamine was higher than that of normal ones in the mass. From the above conclusions, melamine did induce damnification to hippocampal neurons, probably in the way of inducing cells to undergo apoptotic processes and disrupting the homeostasis of Ca2+. Our experimental results disproved some viewpoints that not melamine alone, but melamine and cyanuric acid in combination could cause damage in toxicological studies and provided compelling evidence that low levels of melamine exposure may also represent a health risk to nerves, in opposition to the idea that damage of melamine and cyanuric acid in combination were limited to the kidneys.