[Regulation of chick oviduct DNA polymerases by steroid hormones (author's transl)]

DNA polymerase activity was measured in vitro in soluble cytoplasmic and nuclear fractions of chick oviduct, after in vivo hormone stimulation. By twelve hours after a subcutaneous injection of oestradiol, cytosolic and nuclear DNA polymerase activity had increased 2 to 5 fold over control levels ane continued to increase until 24 hours after the injection. Progesterone induced a slight rise in DNA polymerase activity and dihydrotestosterone had no effect. When oestradiol + progesterone were given together, the stimulating effect of oestradiol was cancelled for approximately 14 hours, contrasting with their synergist-c effect on transcription in this system. Various quantities and various sequences of hormone administration were studied, and some of the physico chemical parameters of the enzymes were determined after the different hormone stimulations. The demonstration of a sex steriod dependent regulation of chick oviduct DNA polymerases and the opposite effects of the oestradiol + progesterone combination on replication and on transcription can represent a new approach in the study of the mechanism of action of steroid sex hormones.