[Effects of different doses of x-ray irradiation on the contents of microsomal hemoproteins in the rat liver]. / Vliianie rentgenovskogo oblucheniia v raznykh dozakh na soderzhanie mikrosomnykh gemoproteidov v pecheni krys.

The content of cytochromes P-450 and b5 in microsomal fraction of rat liver was studied at 1, 3, 6, 12 and 24 hours after X-irradiation with doses of 4, 8 and 12 Gy. It was found that post-irradiation changes in the cytochromes content were already observed in the first hours after X-irradiation independently of a dose of ionizing radiation.

Reasons for reduced activities of 17 alpha-hydroxylase and C17-C20 lyase in spite of increased contents of cytochrome P-450 in mature rat testis fetally irradiated with 60Co.

Pregnant rats received whole body irradiation with 2.6 Gy gamma-ray from a 60Co source at Day 20 of gestation. When pups were 4 months old, activities of electron transport system and steroid monooxygenase in tests were assayed. The content of total cytochrome P-450 in the irradiated testes had increased to 170% of that in non-irradiated rats, but NADPH-cytochrome P-450 reductase activity had reduced to 36% of the control. Also, amounts of cytochrome b5 in testicular microsomal fraction were decreased markedly after irradiation, but no significant change of NADH-cytochrome b5 reductase activity was observed in the treated pups. Because both 17 alpha-hydroxylase and C17-C20 lyase activities tended to be decreased by fetal irradiation, testosterone production from progesterone and 17 alpha-hydroxyprogesterone was reduced to about 30% of the control. From these results, it has been suggested that the testicular cytochrome P-450 is radioresistant but steroid monooxygenase activities are reduced after the fetal irradiation. We propose that the discrepancy arises from the marked decrement of NADPH-cytochrome P-450 reductase activity.