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.
National Institute of Radiological Sciences, Chiba-shi Japan.
H
H
Inano
H
H
Ishii-Ohba
K
K
Suzuki
K
K
Ikeda
D019326:17-alpha-Hydroxyprogesterone; D000446:Aldehyde-Lyases / Q000378:metabolism / Q000528:radiation effects; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism / Q000528:radiation effects; D003579:Cytochrome Reductases / Q000378:metabolism / Q000528:radiation effects; D015786:Cytochromes b5 / Q000378:metabolism / Q000528:radiation effects; D004579:Electron Transport / Q000528:radiation effects*; D005260:Female; D005720:Gamma Rays; D006908:Hydroxyprogesterones / Q000378:metabolism; D008297:Male; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011374:Progesterone / Q000378:metabolism; D011833:Radiation Injuries, Experimental / Q000201:enzymology* / Q000473:pathology; D051381:Rats; D011919:Rats, Inbred Strains; D013254:Steroid 17-alpha-Hydroxylase / Q000378:metabolism / Q000528:radiation effects; D013737:Testis / Q000201:enzymology / Q000473:pathology / Q000528:radiation effects*; D014916:Whole-Body Irradiation
D006908:Hydroxyprogesterones; D011374:Progesterone; D019326:17-alpha-Hydroxyprogesterone; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; D013254:Steroid 17-alpha-Hydroxylase; D003579:Cytochrome Reductases; D000446:Aldehyde-Lyases