Hormonal control of ornithine decarboxylase and spermidine spermine N-1-acetyltransferase activities by sex steroid hormones in the uterus of ovariectomized rats

The weight of the uteri of ovariectomized(OVX) rats was drastically increas ed by about 5 times at 1 week after one subcutaneous (s.c.) injection of oe stradiol, but not changed by hydroxyprogesterone administration. The activi ties of ornithine decarboxylase (ODC) and spermidine/spermine N-1-acetyltra nsferase (SAT) in the uterus of OVX rats were controlled by exogenous admin istrations of the sex steroid hormones, oestradiol and/or hydroxyprogestero ne to the OVX rats. ODC activity in the uterus of OVX rats was drastically increased by one s.c. injection of oestrdiol, but not changed by one s.c. i njection of hydroxyprogesterone. On the other hand, SAT activity in the ute rus of OVX rats was reduced to one-third by oestradiol administration, whil e by the hydroxyprogesterone administration the enzyme activity was not cha nged,keeping the control level of SAT activity in the uteri of OVX rats tre ated with the vehicle(sesame oil). It is noteworthy that the patterns of ch anges in ODC activity by these hormone treatments are the reverse of the pa tterns of changes in SAT activity in the uteri of OVX rats. Patterns of ODC activity alteration by these sex hormones were very similar to the pattern s of the organ weight alteration, demonstrating that ODC activity correlate s to the growth of the organ.