Differential Sensitivity of Endocrine and Non-Endocrine Tissues to Cadmium-Induced Lipid Peroxidation and the Protective Role of Melatonin.

Cadmium is a toxic heavy metal classified by the International Agency for Research on Cancer as a human carcinogen and recognized as an endocrine-disrupting chemical. The present study aimed to evaluate tissue-specific susceptibility to cadmium-induced oxidative damage to membrane lipids (lipid peroxidation, LPO) and to assess the antioxidative effects of melatonin in porcine tissue homogenates representing endocrine (the thyroid and the ovary) and non-endocrine (the liver, the kidney, and the brain) organs. Homogenates were incubated with cadmium chloride (CdCl2; 2.5-1000 µM) without/with melatonin (0.1-5.0 mM). Lipid peroxidation was assessed spectrophotometrically by measuring malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA) levels. Cadmium significantly increased LPO in the liver (2.5-1000 μM) and in the kidney (25-1000 μM), whereas no prooxidative effect was observed in endocrine tissues or in the brain. Liver damage was mitigated by melatonin doses as low as 0.1 μM across the 250-1000 μM cadmium range, while protection in the kidney was limited to higher melatonin concentrations (2.5-5.0 mM) against damage induced by 100-1000 μM cadmium concentrations. The findings demonstrate pronounced tissue-specific differences in susceptibility to cadmium-induced oxidative stress and support the potential of melatonin as a preventive agent against heavy metal-induced oxidative stress, particularly in non-endocrine organs.