Physiological concentrations of melatonin and corticosterone affect phagocytosis and oxidative metabolism of ring dove heterophils

A functional connection between the neuroendocrine and the immune systems h as been established. Of particular interest is the finding that hormones su ch as melatonin and corticosterone are able to exert modulating effects on the immune function. Therefore, after determining the circadian rhythms of melatonin and corticosterone, we evaluated the in vitro effect of physiolog ical concentrations of melatonin and corticosterone. separately and togethe r, on the phagocytic function and superoxide anion levels of heterophils in ring dove (Streptopelia risoria), Trials were performed with concentration s corresponding to the nocturnal and diurnal levels reached by each of the hormones (50:300 pg/mL and 100:10 ng/mL for melatonin and corticosterone, d iurnal:nocturnal, respectively). The phagocytes were incubated with the hor mones both alone and concurrently. At the highest (nocturnal) concentration , melatonin augmented phagocytic function and at the same time inducing a f all in superoxide anion levels. At the highest (diurnal) concentration, cor ticosterone also enhanced phagocytic function, but without modifying the ph agocyte oxidative metabolism. In the presence of both hormones, however, wh ether with nocturnal or diurnal concentrations, there was a greater increas e in phagocytic function and a decrease in superoxide anion levels than was produced by either of the hormones alone. In conclusion, our findings sugg est that melatonin and corticosterone may have an additive effect in the mo dulation of phagocytic function.