Suppression of both basal and antigen-induced lipid peroxidation in ring dove heterophils by melatonin

There have been several findings recently concerning melatonin as a free ra dical scavenger and general antioxidant. For instance, in bird heterophils we found that 100 mu M of melatonin decreases superoxide anion levels and m odulates superoxide dismutase activity. This paper sought to study the effe ct of melatonin upon induced oxidative damage in heterophils of the ring do ve (Streptopelia risoria). The concentration of malonaldehyde (MDA) as an i ndex of induced oxidative damage to lipid membranes was tested by colorimet ric assay. A heterophil suspension was co-incubated with and without inert particles (latex beads) as material to be phagocytosed, both alone and in c ombination with 100 mu M of melatonin. Measurements were made at the basal time (0 min), as well as at 15, 30, 45, and 60 min. Protein concentrations were determined by a standardized method using bovine serum albumin as stan dard. Results are expressed as nmol MDA/mg prot. Melatonin clearly reduced the production of MDA, an index of lipid peroxidation. It also annulled the enhancement of MDA levels produced by latex beads. Both effects were obser ved at all the times studied. In conclusion, our findings again show that t he neurohormone melatonin could be useful as an effective pharmacological a ntioxidant. (C) 1999 Elsevier Science Inc.