The appearance of prostaglandins and thromboxane in mouse serum after X irradiation was observed by simultaneous quantitative analysis using gas chromatography/mass spectrometry/selected ion monitoring with stable isotope dilution methods. Mice of two strains (C57BL/CN Jcl and BALB/c) showed similar responses to X irradiation. In C57BL/6N Jcl mice, 0.2 Gy irradiation elicited a significant increase in generation of prostanoids: Immediately after irradiation, the 6-keto PGF(1) alpha:TXB2 ratio and the level of PGE(2) increased, after 20 min 6-keto PGF(1) alpha and PGE(2) increased, and after 4 h PGE(1) and PGE(2) increased. In BALB/c mice, generation of prostanoids was increased significantly immediately after irradiation (6-keto PGF(1) alpha, 6-keto PGF(1) alpha:TXB2 ratio, PGE(2)), and the increase was maintained from 20 min to 4 h (PGE(1), PGE(2)) after 0.2 Gy irradiation. In C57BL/6N Jcl mice, a significant increase in production of 9 alpha,11 beta-PGF(2) was observed at 20 min after irradiation. In BALB/c mice, a significant increase in 9 alpha,11 beta-PGF(2) was seen immediately after irradiation and was maintained for 20 min. In C57BL/6N Jcl mice, the level of 8-epi PGF(2) alpha was clearly increased 4 h after 4 Gy irradiation. A slight and slow increase was also seen after 0.2 Gy irradiation. In BALB/c mice, 8-epi PGF(2) alpha was increased significantly at 20 min and 4 h after 4 Gy irradiation. These results show that 0.2 Gy irradiation stimulates production of prostanoids related to the inflammatory response in mice. (C) 1998 by Radiation Research Society.