Hepatotoxic effects of melamine exposure from the weaning period in rats: a flow cytometric, electron microscopic, and histopathologic study.

This study aims to investigate the effects of melamine exposure from the weaning period (21st postnatal days in rats) on liver tissue. Female Wistar albino rats (n = 18) were divided into three groups. About 0.1-ml saline was applied to the control group by gavage for 21 days from the postnatal 21st day. The second group was taken 50-mg/kg melamine (in 0.1-ml saline) and the third group was taken 75-mg/kg melamine (in 0.1-ml saline) p.o. On the postnatal 45th day, all rats were sacrificed under anesthesia. Then, liver tissues were cut into three parts and two of them placed in neutral formalin for histopathological and flow cytometric analysis, and one of them placed in 2.5% glutaraldehyde. Histopathological analysis was performed with hematoxylin & eosin, Masson trichrome, periodic acid Schiff stained sections, and also with transmission electron microscopy. Apoptosis (Annexin V positivity) was analyzed by flow cytometry. According to histopathological analysis, hepatocyte damage, sinusoidal dilatation, and inflammatory cell infiltration significantly increased in both melamine groups compared with the control group. Apoptosis significantly increased in the 50 and 75-mg melamine groups compared with the control group. In the results of transmission electron microscopy analysis, there was abnormal chromatin distribution in the hepatocyte nuclei, loss in the cristae of the mitochondria, and organelle loss in large areas in the cytoplasm in both melamine exposure groups. As result, melamine exposure from the weaning period causes liver damage with increasing doses.