ACTA ENDOCRINOLOGICA (BUC)

Introduction. Melatonin, the major pineal secretion, regulates sleep/wake cycle and plays an important part in several physiological functions. It is a powerful free\r\nradical scavenger and upregulates several antioxidant enzymes to reduce oxidative stress.\r\nObjective. Mammalian red blood cells contain membrane-bound acetylcholinesterase. Melatonin, being an effective\r\nantioxidant, may cause alteration in erythrocyte acetylcholinesterase activity.\r\nMethods. The study was carried out on 29 healthy donors of both sexes who gave informed consent for the use of their blood samples for the study. The erythrocytes isolated from blood collected at two different timings of the day were subjected to in vitro treatment with melatonin in a concentrationdependent manner followed by the assay of\r\nenzyme activity.\r\nResults. A rhythmic pattern is observed in the activity of acetylcholinesterase, the activity being higher in diurnal samples. Exogenous melatonin modulates the activity of acetylcholinesterase in erythrocytes which is more pronounced at such concentration close to the peak physiological level of melatonin in the body.\r\nConclusion. The increase in the enzyme activity may be explained in relation to the antioxidant potential of melatonin, which is in accordance with the change in photic signals. Further study is required to understand the\r\nmechanism of action.