Comparison between in vitro lipid peroxidation in fresh sheep platelets and peroxidative processes during sheep platelet ageing under storage at 4 degrees C

Incubation of sheep platelet crude membranes with xanthine oxidase (XO)/hyp oxanthine/Fe2+-ADP revealed: (i) a fast peroxidative response - with a maxi mal linear rate of 14 nmol malondialdehyde (MDA) equivalents/mg protein, as evidenced by the thiobarbituric acid test - and a decrease in the polyunsa turated fatty acid (PUFA) content of the platelet crude membranes; (ii) a d ecrease in the lipid fluidity in the deep lipid core of the membranes but n ot at the membrane surface; (iii) a dramatic inhibitory effect on glucose 6 -phosphatase (Glc-6-Pase) but not on acetylcholinesterase activity. Platele ts were also aged by storage at 4 degrees C in their own plasma or in Seto additive solution. In these media, platelet aggregates were visible and the effects on platelet phospholipids, PUFA, lipid extract fluorescence, crude membrane fluidity and membrane-bound enzyme activities were assessed for c omparison with those observed in in vitro lipid peroxidation. The sensitivi ty of membranes from stored platelets to lipid peroxidation was also assess ed. Storage of platelets in plasma for 5 days was associated with different changes in their crude membranes such as decreases in arachidonic acid con tents, the decrease not being avoided by the presence of phospholipase A(2) inhibitors, increases in MDA equivalents, conjugated dienes and lipid extr act fluorescence, decreases in the amounts of MDA equivalents formed by pla telet crude membranes treated with the oxidizing agents, changes in membran e fluidity and inhibition of Glc-6-Pase. All these alterations were less pr onounced or even abolished after platelet storage in Seto. These findings s uggest that platelet lipid peroxidation due to XO/hypoxanthine/ Fe2+-ADP an d platelet membrane alterations observed after platelet ageing under storag e at 4 degrees C share common features. Also, as regards the prevention of peroxidative processes, Seto solution permits better storage of sheep plate lets than plasma. (C) 1999 Elsevier Science B.V. All rights reserved.