Inverse relationship between poly (ADP-ribose) polymerase activity and 2',5'-oligoadenylates core level in estrogen-treated immature rat.

The activity of poly (ADP-ribose) polymerase (ADPRP) and the content of 2',5'-oligodenylates core (2',5'An; n = 2,3 and 4) were measured in homogenates of the uterus and of the liver of immature rats immediately before (time 0) or at different times after injection of estradiol-valerate. ADPRP activity increased gradually, starting 6 hours after estrogen injection, for about 4 days. Instead, the content of 2',5'An decreased by about 50% within 6 hours, and thereafter more slowly for 4 days to about 20% of starting values. Estrogen increased ADPRP activity and decreased 2',5'An concentration also in the kidney and in the cardiac muscle of the same animals, but not in the skeletal muscle, where neither of the two parameters was affected. Injection of vehicle only (sesame oil) had no effect on ADPRP activity nor on 2',5'An content of immature rat tissues.