Nitric oxide is not related to cadmium-induced oxidative damage in wheat leaves.

ROSALES EP, GROPPA MD, BENAVIDES MP

Mar del Plata, Argentina

Congreso; XLIII Reunion Anual Sociedad Argentina de Investigacion en Bioquimicay Biologia Molecular (SAIB); 2007

SAIB

The mechanisms involved in cadmium toxicity have not been completely elucidated. In wheat roots, cadmium induced nitric oxide (NO) formation and this molecule seemed to be related to the oxidative damage caused by the metal. The aim of this work was to evaluate if the same process that occur in roots is operating in leaves. Wheat leaf segments were incubated for 3 or 21 h in a rotatory shaker with either 500 ìM Cd2Cl or 10, 100 or 500 ìM SNP, used as NO donor. Electrolyte leakage was increased 105% by Cd2+ after 3h or 21h, but NO increased cell membrane damage only when used at 500 ìM. However, whereas at 21h Cd2+ increased TBARS by 25 %, NO 100 or 500 ìM reduced damage to lipids by at least 50%. Chlorophyll content was slightly diminished by all treatments at 21h, except by 10 ìM NO. Detoxification of H2O2 was evaluated by estimating different H2O2 decomposing enzymes. Nitric oxide significantly increased ascorbate peroxidase at higher concentrations, while Cd2+ reduced its activity by around 20% at 3h and 21h. Catalase activity was also increased by 100 and 500 ìM NO after 21h of treatment. These preliminary results suggest that NO is performing a protective role by increasing the activity of H2O2 detoxifying enzymes and decreasing TBARS formation compared to non- treated leaf discs, and seemed not to be involved in the oxidative damage produced by cadmium.