Super oxide radical production by microsomal membranes from senescing carnation dianthus caryophyllus flowers an effect on membrane fluidity

Mayak, S.; Legge, R.L.; Thompson, J.E.

Phytochemistry 22(6): 1375-1380


ISSN/ISBN: 0031-9422
Accession: 006542267

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The lipid fluidity of carnation microsomal membranes decreases during in vitro aging in a manner that correlates with enzymatic production of superoxide anion .**GRAPHIC**. by the membranes. Levels of .**GRAPHIC**. were determined from ESR spectra of the semiquinone formed when .**GRAPHIC**. reacts with Tiron (1,2-dihydroxybenzene-3,5-disulfonic acid). Heat denaturation of the microsomes or addition of n-propyl gallate, a free radical scavenger, eliminated the Tiron radical signal and prevented the change in membrane fluidity. By contrast, the addition of xanthine/xanthine oxidase, a reputed .**GRAPHIC**. system, accentuated the decrease in membrane fluidity and greatly increased the Tiron radical signal. Superoxide dismutase, an enzyme that catalyzes the dismutation of .**GRAPHIC**. reduced the amplitude of the Tiron radical signal. When Tiron was used as a scavenger of .**GRAPHIC**. there was no change in membrane fluidity. .**GRAPHIC**. or highly reactive derivatives of .**GRAPHIC**. induce membrane rigidification. In addition, microsomes from senescent flowers produce more .**GRAPHIC**. than those from freshly cut flowers, suggesting that this reactive species of O2 also contributes to membrane rigidification during natural senescence.