Thromboxane increase in irradiated animals is caused by stimulation of cyclooxygenase activity.

The irradiation of whole body of rabbits with a dose of 6.0 Gy causes an increase in thromboxane synthesis from exogenous arachidonic acid. The uptake of [14C]arachidonic acid and the total amount of radioactivity released during collagen stimulated aggregation of platelets are not changed following the exposure of animals. The irradiation changes the relation between released arachidonic acid and synthesized thromboxane. The amount of 12-hydroxyeicosatetraenoic acid remains unchanged. The results indicate that the increase in thromboxane synthesis is not associated with the activation of phospholipase but is caused by stimulation of cyclooxygenase activity.