INFLUENCE OF LIGHT AT "WHITE NIGHTS" AND MELATONIN ON CIRCADIAN RHYTHM OF TOTAL ANTIOXIDANT CAPACITY OF HUMAN SALIVA
The results of our previous experiments indicate that total antioxidant capacity (TAC) of human saliva has a distinct circadian rhythm with maximum in the night and minimum in the daytime. The decrease of amplitude and other parameters of circadian rhythm of TAC of saliva in summer is marked. The aim of the present study was to evaluate an effect of light at night and exogenous melatonin (MT) on this parameter. There were 6 participants in experiments, at which 28 circadian rhythms have been analysed. The method of coulometric titration was used for measuring TAC of saliva. Light at night significantly decreases amplitude (P<0.001) and exogenous MT increases the level of AUC (P<0.05) and mesor (P<0.05). MT <i>in vitro </i>has a highest antioxidant activity among water soluble antioxidants tested (MT, quercetin, ascorbat, mitophen, white lignin, rutin). Pharmacological quantities of MT (0.1%) increases TAC of saliva <i>in vitro </i>as high as three times. The results of calculations indicate that specific TAC of MT is not enough to explain increase in TAC of saliva <i>in vivo </i>conditions. Consequently, MT stimulates biosynthesis and/or redistribution of low-molecular weight antioxidants in the human organism.