FURTHER STUDIES ON THE UPTAKE OF LABELLED PROGESTERONE BY THE HYPOTHALAMUS AND PITUITARY OF RATS

Abstract

In a previous paper (Seiki, Higashida, Imanishi, Miyamoto, Kitagawa & Kotani, 1968), it was briefly reported that specific progesterone-binding receptors probably do not exist in the hypothalamus and pituitary gland, because these sites did not show selective uptake of progesterone compared with other parts of the brain after i.v. administration of [3H]progesterone to rats ovariectomized in dioestrus 2 weeks before. Other workers (Watanabe, Saha & Layne, 1968) have failed to show any selective uptake of tritiated norethindrone by the hypothalamus and pituitary gland. To confirm these results, two further experiments have been carried out as follows. Female Wistar rats (about 200 g. body weight) exhibiting 4-day oestrous cycles, as determined by vaginal smears, were used. In expt 1, the animals in four stages of the oestrous cycle were each given an i.v. injection of 30 μc (1·7 × 10−3 μmole) [7α-3H]progesterone (sp. act. 18·1 c/μmole)in 0·2