55-7 |
Oxidation of skeletal muscle homogenate by peroxynitrite |
R. G. BRANNAN and E. A. Decker. Dept. of Food Science & Human Nutrition, Univ. of Massachusetts, Amherst, Chenoweth Bldg., Amherst, MA 01003 Peroxynitrite (ONOO) is a reactive nitrogen species formed from the reaction between nitric oxide and superoxide and could be an important prooxidant in muscle foods. The potential for nitric oxide and superoxide production are found in skeletal muscle but the participation of peroxynitrite in post-mortem skeletal muscle oxidation is uncharacterized. The objective of this research was to determine if exogenous peroxynitrite could promote lipid oxidation in skeletal muscle homogenate. Skeletal muscle homogenate from trout was oxidatively challenged with reagent peroxynitrite and formation of thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides (LOOH) were monitored. Skeletal muscle homogenate oxidized by reagent peroxynitrite (0.5 mM) was concentration-dependant and exhibited gradual oxidation with time. A 15-fold increase in formation of LOOH and a 9-fold increase in TBARS was observed in skeletal muscle homogenates oxidized over the range of 0 to 0.5 mM peroxynitrite. CO2 (1 mM) suppressed reagent peroxynitrite (0.5 mM) induced formation of LOOH and TBARS by 70% and 68%, respectively, after 4 hr of oxidation. The metal chelators bathophenanthroline-disulfonic acid (BPS; 100 M) and diethylenetriaminepentaacetic acid (DTPA; 100 mM) suppressed but did not completely inhibit oxidation. TBARS concentration was significantly lower at pH 7.2 than 5.6, however, formation of LOOH increased from pH 7.2 to 5.6. These results show that peroxynitrite induces oxidation in skeletal muscle that is suppressed, but not completely inhibited, by CO2, metal chelators, and low pH. This data suggests that peroxynitrite can a) initiate oxidation in its own right or b) enhance oxidation rates by inactivation of endogenous antioxidants or activation of endogenous prooxidants. Since peroxynitrite can potentially increase lipid oxidation in skeletal muscle, characterizing the role of peroxynitrite as a lipid oxidation initiator could provide new insights into the oxidative stability of muscle foods.
Session 55, Muscle Foods: Fresh Meat Quality
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