The rate of lipid peroxidation was determined by measuring the primary products of lipid peroxidation — conjugated diene formation. Mitochondria were incubated in a medium containing 175 mM KCl and 25 mM Tris-HCl (pH 7.4). To determine the lipid peroxidation as a function of different mitochondrial respiratory chain complexes, different substrates were used. Malate was used to study complex I, succinate to study complex II, NADH to study complex III, and ascorbate+TMPD to study complex IV.
The data obtained showed that if electron transfer occurred through complexes I, II or III in mitochondria isolated from non-stressed maize shoots, the rate of lipid peroxidation was equal and rather low (Fig. 1). At complex IV function, the rate of lipid peroxidation was about 50% higher (Fig. 1). These results can be caused by the fact, that at the first two complexes electrons are transferring through the ubiquinone complex, which in plants can function as an effective antioxidant system (Pobezhimova, Voinikov, Membr. Cell Biol., 13:1—8, 2000).
The study of an influence of low-temperature stress on the rate of lipid peroxidation at different respiratory chain complexes function in mitochondria isolated from stressed (4 C, 1 h) maize shoots showed that low-temperature stress increased dienic conjugates formation associated with function of all respiratory chain complexes. The most pronounced increase (about 75%) was detected for complex IV (Fig. 1).
Thus, based on the data obtained, one can conclude that in maize mitochondria, unlike mammals, the highest lipid peroxidation was associated with complex IV function. Cold stress caused a detectible increase of lipid peroxidation at complexes I, III and especially IV function.
1. An influence of cold stress (4 C for 1 h) on lipid peroxidation
in mitochondria isolated from maize shoots.
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