MELATONIN CONTROLS SUPEROXIDE ANION LEVEL - MODULATION OF SUPEROXIDE-DISMUTASE ACTIVITY IN RING DOVE HETEROPHILS

The pineal gland and the immune system in mammals and birds are functi onally connected, with some recent findings showing that melatonin, th e major secretory product of the pineal gland in vertebrates, is a fre e-radical scavenger and general antioxidant. In birds, heterophils, wi th their ability to ingest and kill different antigens, play a central role in the host defense mechanism. This in vitro study investigated the possible antioxidant action of melatonin in heterophils isolated f rom adult male and female ring dove (Streptopelia risoria). The supero xide anion levels (O-2(radical anion)) and the superoxide dismutase (S OD) activity were evaluated as indicators of the metabolic burst of he terophils after ingestion of inert particles (latex beads) at the basa l time (0 min) and 15, 30, 45, and 60 min of incubation with 100 mu M melatonin. The heterophil O-2(radical anion) levels, measured by the n itroblue tetrazolium reduction test, were lower after incubation in th e presence of melatonin at all the times studied, a time-dependent eff ect. Latex beads produced a significant increase in SOD activity, wher eas there was a significant decrease in the presence of melatonin. In addition, when heterophils were incubated in the presence of both late x beads and melatonin, the indole appeared to annul the enhancement of SOD activity (U-525nm) produced by latex beads. In conclusion, our fi ndings show that the neurohormone melatonin could be a useful antioxid ant.