The differences in 12-hydroxyeicosatetraenoic acid and thromboxane B2 release from guinea pig platelets

Anti-12(S)-hydroxyeicosatetraenoic acid (12-HETE)-antibody and anti-thromboxane B2 (TXB2)-antibody were generated and applied to the radioimmunoassay. The detection limit for 12-HETE was 16 pg. The cross-reactivities of anti-12-HETE-antibody were 4.6% for 15-HETE, 0.18% for 5-HETE and below 0.15% for leukotrienes and prostaglandins (PGs). 12-HETE and TXB2 released from guinea pig platelets were measured by radioimmunoassay. Platelet activating factor (PAF) at 10(-9) M induced the aggregation of platelets, the releases of immunoreactive-12-HETE (1.8 +/- 1.2 ng/10(8) platelets, mean +/- S.D.) and immunoreactive-TXB2 (18.5 +/- 17.3 ng/10(8) platelets). Collagen at 1 microgram/ml also evoked platelet aggregation, the releases of immunoreactive-12-HETE (2.7 +/- 1.1 ng/10(8) platelets) and immunoreactive-TXB2 (11.8 +/- 4.6 ng/10(8) platelets). By the stimulation with these compounds, TXB2 was produced in a greater amount than 12-HETE from guinea pig platelets. Although 10(-7) M and 10(-6) M U46619, a TXA2 mimetic, caused platelet aggregation, arachidonic acid metabolites were not released. These data suggest the presence of different mechanisms of platelet activation depending on each stimulus.