Aim: 

To examine the effect of the pineal indole melatonin and its precursor, the amino acid tryptophan, on lipid peroxidation and superoxide dismutase activity in heterophils from young (4-5 yr) and old (12-14 yr) ringdoves (Streptopelia risoria) in both basal and antigen-induced conditions.

Methods: 

Animals were kept under a 12:12 h light/dark cycle and fed ad libitum. Young animals were treated for 3 consecutive days with a single daily oral dose (0.25 mg) of melatonin one hour before lights off (19:00). Old animals were treated for 3 consecutive days with either a single daily oral dose (2.5 mg) of melatonin one hour before lights off or a single oral capsule of 300 mg/kg b.w. of L-tryptophan at 09:00 (one hour after the onset of the light period). Heterophil leukocytes were obtained immediately after the collection of 1 ml of blood at day and night and were incubated for 45 min with or without inert particles (latex beads). Malondialdehyde levels (MDA), as an indicator of lipid peroxidation (LPO), and superoxide dismutase activity (SOD) were determined using commercial kits.

Results: 

In basal conditions, old animals presented higher levels of malondialdehyde levels at both day and night. In both groups of age, LPO levels were lower at night than during the day. In a general fashion, melatonin and tryptophan treatments reinforced the SOD activity, as well as reducing the MDA levels induced by the antigen.

Conclusion: 

Melatonin and tryptophan may be useful agents for the treatment of disease states and processes in which a higher production of oxidative damage is produced.

Supported by Junta de Extremadura (3PR05A053). S.D. Paredes, I. Bejarano and MP. Terrón are beneficiaries of grants by Junta de Extremadura (POS07012, PRE06070 and REI07004, respectively).