Zinc (Zn2+) at low levels may play several basic housekeeping functions in metalloenzymes, transcription factors and cell signaling proteins. As a consequence Zn2+ might play important physiological roles regulating cell growth and neurotransmission. Additionally, it may play antioxidant, anti-apoptotic and anti-inflammatory activities in diverse cell models of central nervous system. On the other hand, high levels of Zn2+ might be toxic to the cells. The aim of this study was to investigate the effect of Zn2+ over the activity of antioxidant enzymes in hippocampal slices of immature rats. The hippocampi were isolated from immature Wistar rats (14 days old) and they were incubated for 2 hours in Hepes-saline buffer in absence (control) or presence of Zn2+ (10-300mM). Further, the slices were homogenized in HEPES 20mM, pH 7.0 and centrifuged at 20.000 X g for 30 minutes. The supernatant was collected to measure the antioxidant enzyme activities, including: glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione S-transferase (GST). The pellet was resuspended in Tris/HCl 0.05M, pH 7.4 in order to determine to gamma-glutamyl transpeptidase (GGT) activity. The results indicate that Zn2+, at all concentrations tested (10-300mM) significantly inhibited GR activity. The higher effect on GR was achieved at concentrations up to 100mM. The activities of GPx, GST and GGT were not affected by Zn2+. The significant inhibition of GR by Zn2+ observed in our study, indicates GR as a possible mechanism of Zn2+ toxicity, and open perspectives to further investigate the mechanisms underlying Zn2+ neurotoxicity.

Support by IFS grant W/3636 (ALD), CNPq, UFSC, CAPES fellowships to JLF, TP, CSO and PROCAD/CAPES.