The generation of the F-2-isoprostane 8-epi-PGF(2 alpha) by human platelets on collagen stimulation

F-2-isoprostanes are prostaglandin (PG) F-2-like compounds formed via non-e nzymatic peroxidation of arachidonic acid, although some F-2-isoprostane pr oduction may be cyclo-oxygenase (COX)-mediated, Of these substances 8-epi-p rostaglandin F-2 alpha (8-epi-PGF(2 alpha)) has received the most attention as it induces vasoconstriction and mitogenesis, and influences pathophysio logical mechanisms relevant to arterial disease. Using improved methods for F-2-isoprostane determination we examined collagen-stimulated platelet pro duction of F-2-isoprostanes in platelet-rich plasma (PRP), distinguishing b etween the free and esterified forms of these substances. Collagen stimulat ion caused marked release to the plasma (platelet-poor; PPP) of free 8-epi- PGF(2 alpha) (2 +/- 2 pg/mg platelet protein vs 174 +/- 53 pg/mg protein, c ontrol (i.e. non-stimulated) vs collagen-stimulated, P < 0.05) and of free 9 alpha,11 alpha-PGF(2 alpha), (37 +/- 19 pg/mg protein vs 1948 +/- 643 pg/ mg protein, control vs stimulated, P < 0.05), a COX derived product. Neithe r free nor esterified 9 alpha,11 beta-PGF(2 alpha) and 9 beta,11 alpha-PGF( 2 alpha) were detectable in control or collagen stimulated samples. Sample concentrations of the esters of 8-epi-PGF(2 alpha) and 9 alpha,11 alpha-PGF (2 alpha) were unaltered by collagen stimulation. These data confirm a prev ious report that activated platelets release the F-2-isoprostane 8-epi-PGF( 2 alpha), accompanying the release of a COX-derived product, 9 alpha,11 alp ha-PGF(2 alpha).