G. Ozturk et al., The effect of melatonin on liver superoxide dismutase activity, serum nitrate and thyroid hormone levels, JPN J PHYSL, 50(1), 2000, pp. 149-153
Melatonin is a main neurohormone of the pineal gland. The effects of melato
nin on the level of serum thyroid-stimulating hormone (TSH), thyroxine (T-4
), triiodothyronine (T-3), nitrate, melatonin and liver superoxide dismutas
e (SOD) activity were examined in rats. Melatonin was injected at the dose
of 10 mg/kg for 7 days, 2 h before turning the lights off. Rats were decapi
tated at 10:00 a.m, and 02:00 a.m., which are the times of the lowest and h
ighest serum melatonin levels, respectively. Blood and tissue samples were
collected. Decreased TSH, T-3, T-4 and nitrate levels were determined in th
e melatonin-injected and nighttime groups. Melatonin levels showed a diurna
l rhythm. SOD activity increased in the melatonin-treated group. The result
s demonstrate that increased SOD activity, and reduced serum TSH, T-3, T-4
and nitrate levels correlated with the serum melatonin levels.