Effects of estradiol benzoate and progesterone on superoxide dismutase activity in the thymus of rats

The activity of mitochondrial superoxide dismutase (MnSOD) and cytosol supe roxide dismutase (CuZnSOD) was measured in corresponding subcellular fracti ons prepared from the thymi of intact and chronically gonadectomized (GX) r ats of both sexes, as well as of GX male and female rats injected subcutane ously with a single dose of 5 mug estradiol benzoate (EB) and/or 2 mg proge sterone (P). Animals were sacrificed 2 h or 24 h following hormone treatmen t. In the females, the activity of MnSOD in the thymus was stable during th e estrous cycle and did not change after ovariectomy. Treatment of GX femal es with estradiol benzoate resulted 2 h later in a significant elevation of MnSOD activity, whereas 24 h later the activity returned back to control v alues. On the other hand, treatment of GX females with progesterone had no effect on the MnSOD activity. However, combined hormone treatment, in which EB injection preceded progesterone injection by one hour, enhanced the eff ect on MnSOD activity similar to that of estradiol benzoate alone. The acti vity of CuZnSOD in cycling rats was increased in proestrus, whereas removal of the ovaries kept the values at low diestrus and estrus levels. Contrary to MnSOD, CuZnSOD activity did not change after EB treatment of GX females , while progesterone increased the enzyme activity at 2 h and 24 h after ho rmone treatment. However, combined EB+P treatment proved to be ineffective. In the males, neither MnSOD nor CuZnSOD activity was affected by the remov al of testes or by progesterone treatment of GX animals. Only EB injection to GX rats significantly increased CuZnSOD activity 24 h later.