Cellular and subcellular localization of 3H-oestradiol in the oviduct and uterus of the neonatal rat

Two day old female rats were injected sc with 1.0 μg of 3H-oestradiol per 100 g body weight and killed 2 h later. Oviducts and uteri were removed, mounted on tissue holders, and frozen in liquefied propane. Four μm frozen sections were cut in a cryostat and mounted according to the dry-mount and thaw-mount autoradiographic procedures. The sections were exposed at –15°C for different periods of time, then photographically processed and stained with methyl green-pyronin. Radioactivity was found concentrated in nuclei of cells of the luminal epithelium in the uterus, but not in the oviduct, while cells of the connective tissue and muscularis showed nuclear concentration of radioactivity in both organs. Pretreatment with oestradiol inhibited the nuclear concentration of radioactivity, whereas pretreatment with 5α-dihydrotestosterone had no effect. It is concluded that both the uterus and oviduct of the neonatal rat have receptors for oestrogen as early as 2 days after birth.

Neurons of the hypothalamus concentrate (3H)progesterone or its metabolites

Selective concentration of [(1)H]progesterone or its metabolites is observed in nuclei of neurons in certain hypothalamic regions of the guinea pig 15 minutes after injection of [1,2,6,7-(3)H]progesterone, by use of dry-mount autoradiography. Highest concentrations of progestin target neurons exist in the nucleus arcuatus, the nucleus preopticus periventricularis, and the nucleus preopticus suprachiasmaticus. Previous administration of unlabeled progesterone inhibits the nuclear concentration of radioactivity, but cortisol has no effect. Estradiol priming enhances the nuclear uptake of radioactivity. The results demonstrate the existence of progestin target sites in the hypothalamus and suggest a direct action of progestin on certain hypothalamic structures.

Pituitary gonadotrophs: nuclear concentration of radioactivity after injection of ( 3 H)testosterone

Gonadotrophs and castration cells in the male rat pituitary showed nuclear concentration of radioactivity 1 hour after [1,2,6,7-(3)H]testosterone injection. Thyrotrophs and acidophils did not retain radioactivity; also the cells of the intermediate and posterior lobes did not accumulate radioactivity. The autoradiographic results suggest a direct and selective action of androgen on gonadotrophs, which contrasts with the action of estradiol which was shown earlier to bind not only to basophils but to acidophils and chromophobes as well.