Subacute toxicopathological studies of methotrexate in Wistar rats

Aim: A toxico-pathological study was undertaken to assess the effects of Methotrexate administration in Wistar rats by performing the hematology, serum biochemical analysis and associated histopathological changes in visceral organs. Materials and Methods: Rats in 4 treatment groups with 6 male and 6 female rats each were administered methotrexate (Group II to IV) at the dose rate of 0.062, 0.125 and 0.250 mg/kg body weight respectively and distilled water (Group I) as vehicle control for 28 days. Hematological parameters viz., total erythrocyte count, haemoglobin, packed cell volume, MCV, MCH and MCHC, total leukocyte count and differential leukocyte count and serum biochemical parameters viz., aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, serum creatinine, blood urea nitrogen, total protein, albumin, globulin (Calculated) were estimated after 28 days. Necropsy examination was performed in all sacrificed animals and gross lesions were recorded. Tissue samples (lung, liver, kidney, intestine, testes and heart) were collected in 10% formalin solution for histo-pathological examination. Results: The dose dependent reduction in body weight, feed consumption, RBCs count, packed cell volume, haemoglobin, total leucocyte count, neutrophil count, total protein and albumin was observed in animals of group II, III and IV along with significant increase in lymphocyte count, AST, ALT, AKP, creatinine and BUN in animals of methotrexate treated group IV followed by group III. No significant change in monocyte, eosinophil and basophil counts were observed in any treatment groups. All the rats exposed to methotrexate at three different dose levels revealed dose dependent pathological changes characterized by degeneration, necrosis, congestion, haemorrhage and vascular changes. The main target organs affected were liver, kidney, lungs and testes. Conclusion: It can be concluded from this study that sub-acute exposure to methotrexate produced no appreciable changes at recommended 0.062 mg/kg body weight dose level. The findings observed at 0.250 mg/kg body weight methotrexate dose level are of public health significance and regulatory importance due to its hepatotoxic and nephrotoxic character.