Zinc coadministration attenuates melatonin's effect on nitric oxide production in mice

Both melatonin (MEL) and zinc (Zn) are considered beneficial for anti-immun osenescence. MEL's effects on immune functions are partly attributed to an interaction with Zn. However, the augmentation of or interference with MEL' s effects by coadministration of Zn remains unclear. in this study, adult o lder mice received either MEL (10 mu g/mL), Zn (22 mu g/mL), MEL+Zn, or nul l supplementation from drinking water for 3 mo. The results showed that tre ated mice, irrespective of the type of added chemicals, had higher body-wei ght gain and body-fat content than control mice. MEL- and Zn-treated mice a lso had increased serum free fatty acid levels. In addition, the MEL group had decreased serum NOx (nitrite+nitrate) values. Serum tumor necrosis fact or-alpha levels were increased, although nonsignificantly, in mice that rec eived either MEL or Zn supplementation. However, the differences described were not retained in the mice that received MEL+Zn treatment. We conclude t hat a high-dose Zn coadministration might exert negative influences on MEL' s regulatory effects, at least on nitric oxide production.