Effects of melatonin on the Harderian gland of lipopolysaccharide-treated rats: morphological observations

Melatonin is a free radical scavenger and antioxidant. This indol is report ed to efficiently scavege both hydroxyl and peroxyl radicals and it also re duces both in vitro and in vivo tissue damage due to oxidants which generat e oxygen toxic radicals. Lipopolysaccharide (LPS) administration induces ox idative damage in various tissues mainly due to its ability to increase rea ctive oxygen species. In the present work, we studied the morphological cha nges and lipid peroxidation in the Harderian gland after LPS administration and the effects of melatonin in preventing the induced changes. Hyperchrom asia, vesicular degeneration, necrosis and infiltration with macrophages, m onocytes and neutrophils were observed in the LPS-treated group (10 mg/kg, intraperitonally [ip]). Also, a typical structure of the glandular acini of the gland exhibited diffuse damage. In the LPS rats heated with melatonin (10 mg/kg, ip), a diminished number of infiltrative cells was seen, and clo udy swelling was reduced, as was nuclear hyperchromasia. Neither necrosis n or vesicular degeneration were noted in the melatonin-treated rats, and in general, glandular structure was preserved. Lipid peroxidation products inc reased significantly within six hours after LPS administration, and melaton in treatment decreased the LPS-dependent lipid peroxidation products. These data together suggest that melatonin protects the Harderian gland against LPS toxicity in terms of morphological damage. (C) 1999 Editions scientifiq ues et medicales Elsevier SAS.