Irradiation of rats abolishes susceptibility of PGI2 synthesis in blood vessels to peroxidative agents

Thoracic and abdominal aortas were obtained from rats after irradiation and used for the estimation of the synthesis of prostacyclin (PGI2) determined as 6-keto PGF1 alpha. Twenty four h after exposure to 7.0 Gy an increase was noted in the amount of PGI2 released, and 4 weeks later its level significantly decreased. The 24 h value did not increase with the further radiation dose increment (9, 12.5, 15 Gy). Cysteine or H2O2 intensified prostacyclin synthesis in control vessels but decreased it in vessels from the animals irradiated 24 h earlier. Later after the exposure cysteine or H2O2 were no longer effective.