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Melatonin reduces high levels of lipid peroxidation induced by potassium iodate in porcine thyroid

2019; Hogrefe Verlag; Volume: 91; Issue: 3-4 Linguagem: Inglês

10.1024/0300-9831/a000628

1664-2821

Paulina Iwan, Jan Stępniak, Małgorzata Karbownik‐Lewińska,

Vitamin K Research Studies

Abstract. Iodine is essential for thyroid hormone synthesis. Under normal iodine supply, calculated physiological iodine concentration in the thyroid is approx. 9 mM. Either potassium iodide (KI) or potassium iodate (KIO 3 ) are used in iodine prophylaxis. KI is confirmed as absolutely safe. KIO 3 possesses chemical properties suggesting its potential toxicity. Melatonin (N-acetyl-5-methoxytryptamine) is an effective antioxidant and free radical scavenger. Study aims: to evaluate potential protective effects of melatonin against oxidative damage to membrane lipids (lipid peroxidation, LPO) induced by KI or KIO 3 in porcine thyroid. Homogenates of twenty four (24) thyroids were incubated in presence of either KI or KIO 3 without/with melatonin (5 mM). As melatonin was not effective against KI-induced LPO, in the next step only KIO 3 was used. Homogenates were incubated in presence of KIO 3 (200; 100; 50; 25; 20; 15; 10; 7.5; 5.0; 2.5; 1.25 mM) without/with melatonin or 17ß-estradiol. Five experiments were performed with different concentrations of melatonin (5.0; 2.5; 1.25; 1.0; 0.625 mM) and one with 17ß-estradiol (1.0 mM). Malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA) concentration (LPO index) was measured spectrophotometrically. KIO 3 increased LPO with the strongest damaging effect (MDA + 4-HDA level: ≈1.28 nmol/mg protein, p < 0.05) revealed at concentrations of around 15 mM, thus corresponding to physiological iodine concentrations in the thyroid. Melatonin reduced LPO (MDA + 4-HDA levels: from ≈0.97 to ≈0,76 and from ≈0,64 to ≈0,49 nmol/mg protein, p < 0.05) induced by KIO 3 at concentrations of 10 mM or 7.5 mM. Conclusion: Melatonin can reduce very strong oxidative damage to membrane lipids caused by KIO 3 used in doses resulting in physiological iodine concentrations in the thyroid.