Human plasma concentrations of malondialdehyde (MDA) and the F2-isoprostane 15(S)-8-iso-PGF2α may be markedly compromised by hemolysis: Evidence by GC-MS/MS and potential analytical and biological ramifications

Objectives:Malondialdehyde (MDA) and the F2-isoprostane 15(S)-8-iso-prostaglandin F2α (15(S)-8-iso-PGF2α) belong to the most frequently analyzed biomarkers of oxidative stress in basic and clinical research. The objective of the present study was to examine the effect of hemolysis on free MDA and total (free + esterified) 15(S)-8-iso-PGF2α concentrations in human plasma.Design and methods:MDA and 15(S)-8-iso-PGF2α were determined by GC-MS/MS in plasma samples from venous heparinized blood drawn under resting conditions (n = 22) as well as under physical exercise (n = 158) in 22 healthy young subjects. In vitro, we prepared plasma samples with hemolysis degrees up to 0.8% using artificially hemolyzed, freshly obtained heparinized blood.Results:In some plasma samples of the exercise study both under resting and exercise conditions, clinically significant hemolysis was macroscopically visible. Both in vivo (r = 0.74) and in vitro (r = 0.87), we found a significant positive correlation between hemolysis degree (0–0.2%) and MDA plasma concentrations (50–250 nmol/L). Unlike in vitro (r = 0.84), in vivo, 15(S)-8-iso-PGF2α and MDA plasma concentrations correlated weakly (r = 0.50).Conclusions:We hypothesize that free hemoglobin catalyzes the formation of MDA and 15(S)-8-iso-PGF2α from free and esterified arachidonic acid. Plasma concentrations of MDA and total 15(S)-8-iso-PGF2α may be markedly compromised by hemolysis. Measurements of MDA and 15(S)-8-iso-PGF2α should be treated with caution regarding involvement of oxidative stress in disease as well as in health both under resting conditions and under exercise.