Polyamines as protectors against cadmium or copper-induced oxidative damage in sunflower leaf discs

Polyamines antioxidant properties were studied in sunflower leaf discs under cadmium and copper induced oxidative stress. Both metals induced oxidative damage in the studied tissue, as evidenced by an increment in lipid peroxidation and a decrease in antioxidant enzymes ascorbate peroxidase (APOX), glutathione reductase (GR) and superoxide dismutase (SOD) activities. Polyamines concentrations were differently affected according to the metal used. Putrescine (Put) was reduced 52% by Cd2+ and 39% by Cu2+, spermidine (Spd) was decreased to 21 and 59% of the control by Cd2+ and Cu2+, respectively and spermine (Spm) content was not modified by any of the metals. Pretreatment with exogenously added polyamines (1 mM) showed that Spm reverted the effect of Cd2+ and Cu2+ on lipid peroxidation almost to control values. Neither Spm nor Spd recovered the metal-reduced APOX activity. Besides, both polyamines affected this parameter by themselves. GR activity was completely restored by Spm or Spd and only Spm was effective in reverting copper-reduced SOD activity. This work suggests that polyamines are undoubtedly related to the protection against metal-induced oxidative stress, but more research is necessary to elucidate the precise role they played as antioxidants. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.