Endocrine Abstracts (2008) 16 P295

Melatonin restores the basal level of lipid peroxidation in rat tissues under conditions of exposure to potassium bromate

Magdalena Stasiak3, Andrzej Lewinski2 & Malgorzata Karbownik-Lewinska1

1Department of Oncological Endocrinology, Medical University of Lodz, Lodz, Poland; 2Department of Endocrinology and Metabolic Diseases, Medical University of Lodz, Lodz, Poland; 3Department of Endocrinology and Metabolic Diseases, Research Institute, Polish Mother’s Memorial Hospital, Lodz, Poland.

Potassium bromate (KBrO3) is a known prooxidant and carcinogen. Melatonin is a highly effective antioxidant. Indole-3-propionic acid (IPA) – an indole substance, and propylothiouracil (PTU) – an antithyroid drug, also reveal some antioxidative effects. The aim of the study was to evaluate KBrO3-induced lipid peroxidation in vitro in tissues collected from either control or melatonin-treated rats, and to compare potential preventive effects of melatonin, IPA and PTU.

Kidney, liver and lung homogenates from either the control or the melatonin-treated rats (0.0645 mmol/kg b.w., i.p., twice daily, for 10 days) were incubated in the presence of KBrO3 (0.1, 0.5, 1.0, 2.5, 5.0, 10.0 mM). As prooxidative effect of KBrO3 was observed only in the control lung homogenates, they were then incubated in the presence of KBrO3 (10.0 mM) plus melatonin (0.01, 0.1, 0.5, 1.0, 5.0, 7.5 mM), or IPA or PTU (0.01, 0.1, 0.5, 1.0, 5.0, 7.5, 10.0 mM). The level of lipid peroxidation products – malondialdehyde +4-hydroxyalkenals (MDA+4-HDA) – was measured spectrophotometrically.

KBrO3 treatment increased lipid peroxidation in the control lung homogenates, but not in the lung from the melatonin-treated rats. Melatonin, IPA and PTU reduced KBrO3-induced lipid peroxidation. Unexpectedly, KBrO3 caused a concentration-dependent decrease in lipid peroxidation in liver and kidney homogenates from the control rats, whereas such an effect was less pronounced in tissues from the melatonin-treated rats.

In conclusion, KBrO3-induced lipid peroxidation in rat lung suggests that it may be the target organ for this carcinogen. An exposure of an organism to melatonin decreases tissue sensitivity to KBrO3-induced damage, possibly by restoring the oxidative balance. Thus, melatonin could be recommended for its possible cancer prevention effects.

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