Objectives: This study aimed to investigate histological and biochemical changes in the livers of formaldehyde exposed rats and possible effects of melatonin hormone on these changes.

Materials and Methods: A total of 21 male Wistar-albino rats were divided into three equal groups. Control rats in Group I received 0.9% NaCl alone intraperitoneally (ip), rats in Group II were injected with 10% formaldehyde (10 mg/kg, ip) every other day and rats in Group III received melatonin (25 mg/kg, ip) plus formaldehyde. At the end of 14-day experimental period, all animals were decapitated. The liver tissue samples were processed histologically and analyzed under light microscope. Additionally, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), xanthine oxidase (XO), and malondialdehyde (MDA) levels in the liver tissue samples were determined.

Results: SOD, GSH-Px, CAT, XO and MDA levels of formaldehyde exposed rats were significantly higher than those of the control group rats. However, these biochemical values of rats treated with melatonin plus formaldehyde were lower than the non-melatonin group. Light microscopic evaluation of liver tissue samples of formaldehyde-exposed rats revealed enlarged sinusoids filled with blood and mononuclear cell infiltration in the portal areas and around the central veins. In addition, some of the hepatocytes showed vacuolar degeneration, and some had a hyperchromatic nucleus. In PAS staining, the hepatocytes around the portal areas were PAS negative. The rats treated with melatonin plus formaldehyde had somewhat fewer histological changes induced by formaldehyde exposure.

Conclusion: The liver damage caused by formaldehyde may be partially prevented by melatonin administration. ©2008, Firat University, Medical Faculty