The present study demonstrates that DNA fragmentation, nuclear pycnosis and trypan blue staining of irradiated thymocytes is prevented by inhibition of the lipoxygenase pathway of arachidonic acid metabolism and is not affected by cyclooxygenase inhibition. Exposed to irradiation [3H]arachidonic acid-labeled thymocytes release radioactive products to the external medium. The process is blocked by the lipoxygenase inhibitor, nordihydroguaiaretic acid. Thus, it can be concluded that irradiation activates arachidonic acid metabolism and that lipoxygenase metabolites play an important role in thymocyte apoptosis.
