Transient responses of melatonin to stress

Abstract

Melatonin and its metabolites are ubiquitous antioxidants that are produced
 in response to reactive oxygen species (ROS) in virtually all cells of the
 body. The highest reported melatonin values in plasma and sweat occur during
 heavy exercise both indoors and outdoors during the day. The advent of sweat
 biosensors with sufficient melatonin sensitivity provides pseudo real-time
 evidence that melatonin is produced throughout the body not just in the pineal
 gland. The role of the pineal gland appears to be to provide cyclic production
 of melatonin for the regulation of circadian rhythms as well as supplemental melatonin
 during periods of low cellular activity. 
 Melatonin from the pineal gland represents only a small fraction of the
 body’s production capacity. Greater than 5 pg/ml min ramp rates for plasma and
 sweat melatonin have been reported during strenuous exercise in sunlight as
 compared to 0.15 pg/ml min ramp rates for plasma melatonin under dim light
 melatonin onset (DLMO) conditions. Sunlight
 and exercise, like fever, generates transient elevated levels of ROS in tissues
 with time constants measured in minutes or even seconds making this systemic
 antioxidant response potentially protective. Based on a simple accounting of
 ROS generated by sunlight, ROS we breathe, ROS we drink, and exercise, it
 appears that the body maintains a heightened basal level of ROS as part of its
 pathogen defense mechanisms. Current
 human lifestyles and modern enclosed spaces have substantially eliminated over
 90% of the ROS which undermines one of the body’s primary defenses. With
 advanced age, the inability to maintain this protective barrier appears to make
 us more susceptible to disease.