Radiation Effects on Testes: XIII. Studies on Isocitrate Dehydrogenases Following Partial-Body Gamma Irradiation

The effect of gamma radiation on NAD- and NADP-linked isocitrate dehydrogenases of testes results in a biphasic response both after lethal and sublethal exposures of 2000 and 720 R. The initial decrease in the activity of these enzymes seems to be associated with both germ and nongerm cells whereas the recovery of the two enzyme activities at a later stage seems to be associated with the hypertrophy of interstitial tissue. The biphasic response of NADP-linked isocitrate dehydrogenase following irradiation has been related to the androgen synthesizing capacity of irradiated testes. NADP-linked isocitrate dehydrogenase is inhibited in both sham-irradiated and irradiated testes after administration of testosterone under various conditions of radiation injury, suggesting that testicular NADP-isocitrate dehydrogenase is under the control of pituitary gonadotrophins. However, independent action of actinomycin D and testosterone propionate in conjunction with irradiation also indicate that mechanisms exist in testes which control the NADP-linked enzyme by local factors.