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

F(2)-isoprostanes are prostaglandin (PG) F(2)-like compounds formed via non-enzymatic peroxidation of arachidonic acid, although some F(2)-isoprostane production may be cyclo-oxygenase (COX)-mediated. Of these substances 8-epi-prostaglandin F(2)alpha (8-epi-PGF(2alpha)) has received the most attention as it induces vasoconstriction and mitogenesis, and influences pathophysiological mechanisms relevant to arterial disease. Using improved methods for F(2)-isoprostane determination we examined collagen-stimulated platelet production of F(2)-isoprostanes in platelet-rich plasma (PRP), distinguishing between the free and esterified forms of these substances. Collagen stimulation caused marked release to the plasma (platelet-poor; PPP) of free 8-epi-PGF(2alpha) (2 +/- 2 pg/mg platelet protein vs 174 +/- 53 pg/mg protein, control (i.e. non-stimulated) vs collagen-stimulated, P < 0.05) and of free 9alpha ,11alpha-PGF (37 +/- 19 pg/mg protein vs 1948 +/- 643 pg/mg protein, control vs stimulated, P < 0.05), a COX derived product. Neither free nor esterified 9alpha, 11beta-PGF and 9beta, 11alpha-PGF(2alpha) were detectable in control or collagen stimulated samples. Sample concentrations of the esters of 8-epi-PGF(2alpha) and 9alpha, 11alpha-PGF(2alpha) were unaltered by collagen stimulation. These data confirm a previous report that activated platelets release the F2-isoprostane 8-epi-PGF(2alpha), accompanying the release of a COX-derived product, 9alpha, 11alpha-PGF(2alpha).