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The cell renewal rate and mitotic cycles were studied in the ovarian follicles of normal adult females during dioestrus and oestrus as well as in neonatally androgenized females at the age of 8 to 9 months. Incorporation of tritiated thymidine into nuclear DNA was followed using radioautography. The mitotic index was higher during dioestrus than during oestrus, both in the granulosa and in the theca interna cells. The labelling index during dioestrus was 32.4 per cent for the granulosa and 17.7 per cent for the theca, but there was no incorporation of radioactive thymidine during oestrus. The theca externa did not show any DNA synthetizing activity in either of the cyclic phases. A cell cycle was complete during dioestrus within 17 hours in the granulosa and within 31 hours in the theca interna.The polycystic ovaries of the persistent oestrous rats showed practically no mitotic activity. In three out of 12 animals some synthesis of DNA was obtained, and in one of them the labelling index exceeded that of the normal dioestrous rats.

The effect of testosterone propionate on cell renewal rate and mitotic cycle of castrated mice was investigated. 0.25 mg of the hormone was given thrice at 24 h intervals and 50 μc of 3H-thymidine was injected simultaneously with the last hormone injection. After this the mice were killed at 1 to 2 h intervals. Ventral prostates and seminal vesicles were weighed and the thymidine incorporation into their epithelia determined in radioautograms. A piece of proximal small intestine was used as reference tissue.The labelling index in the castrated control animals was 1.3 for the seminal vesicle; 68 h after testosterone treatment it was 44. The figures for the ventral prostate were 1.9 and 37, and for the small intestine 44 and 57. The mitotic index in the prostate of the experimental animals and that in the intestine of all the animals was 0.5; in the seminal vesicle it was 0.4. The mitotic index in the accessory glands of the control mice was very low. The specific activity of DNA per nucleus was higher in the hormone treated than in the control animals.The cell cycle (TC) in the prostate was shortened from about 900 h to 20 h after testosterone. The synthetic phase (TS) was shortened from 16 to 7 h, presynthetic (TG1) phase from 900 to 10 h, whereas the postsynthetic phase (TG2) remained unchanged. The corresponding figures for the seminal vesicle were: TG2from 4.5 to 0.5 h, TS from 12 to 7 h, TG1from 900 to 10 h and TCfrom 900 to 18 h. The changes in the intestinal epithelium were less marked: TCfrom 22 to 16 h, TSfrom 8.5 to 8 h, TG1from 12 to 6 h, while TG2remained unchanged.

Male rats were injected subcutaneously with 2 mg of cyproterone daily from birth to the 14th postnatal day. At the age of 40 days the animals were polycystic and corpora lutea were absent. There was an increased 37% of the ovarian implants showed distinct corpora lutea indicating cyclic secretion of gonadotrophins; the implants in the control animals were polycystic and corpora lutea were absent. There was an increased interstitial cell stimulating hormone output from the pituitary gland as indicated by the increased amount of 3β-hydroxysteroid dehydrogenase active Leydig cells in the testes of the feminized animals.The in vitrouptake of tritiated testosterone and oestradiol of various tissues was tested on rats, age 4.5 months. The anterior hypothalamus, the rostral middle hypothalamus, the median eminence and the anterior pituitary of the feminized males retained significantly more oestradiol than the cerebral cortex. The oestradiol uptake in these areas also exceeded that of the control animals. Only the median eminence of the cyproterone treated rats concentrated more testosterone than the cerebral cortex. The anterior hypothalamus and cerebral cortex of the feminized male rats were less able to transform tritiated testosterone to dihydrotestosterone or tritiated oestradiol to oestrone, as compared to adult castrated male or female animals, respectively.

Male and female rat foetuses taken two days before birth, newly born or when 2 days old were injected subcutaneously with tritium labelled testosterone or oestradiol. One hour later the accumulation of radioactivity in the cerebral cortex, hypothalamus and anterior pituitary of the foetuses was studied by means of a microcombustion technique in order to process the samples for liquid scintillation spectrometry. The anterior pituitary accumulated the highest amount of radioactivity i. e. about twice the amount recovered in the brain. No difference was found in the radioactivity of the hypothalamus as compared to that of the cerebral cortex. Both steroids were accumulated equally in the tissues investigated. The retention of the radioactivity was higher in the neonatal than in adult rats. However, no sex difference was observed in the binding capacity of the hypothalamus or the pituitary gland of the newly born animals.