Gonadal Steroid Concentrations in Serum and Hypothalamus of the Rat at Birth: Aromatization of Testosterone to 17β-Estradiol*

Abstract

Endogenous concentrations of testosterone (T), 5 alpha-dihydrotestosterone, progesterone (P), and estradiol-17 beta (E2) were determined with specific RIAs in serum and hypothalami of male and female rats before, during, and up to 24 h after birth. In the male, a dramatic and transient increase in T concentration was observed in the serum and the hypothalamus between 0 h in utero and 2 h after delivery. At all times studied, T levels were undetectable in the female. We failed to detect any significant 5 alpha-dihydrotestosterone levels in the serum and the hypothalamus of both sexes. Serum E2 levels decreased between the 21-day fetal stage and 24 h postpartum. However, in males, hypothalamic E2 dramatically increased between 0 h in utero and 1 h after delivery and decreased between 2 and 24 h. This surge was absent in females and males gonadectomized at 0 h, suggesting that this surge is linked to the presence of the testes. E2 was undetectable in the cerebral cortex. P presented the same pattern of declining levels in the male and the female, and no sex difference was noted for the mean concentrations in the serum or the hypothalamus. The fall in P levels and the sudden increase in hypothalamic T and E2 levels could be determinant factors in the initiation of central nervous system sexual differentiation in the rat. The fact that in the male rat, hypothalamic E2 increases during the time when testicular secretions defeminize the brain strengthens the view that E2 mediates some of the effects of T.

Age‐dependent differential expression of genes involved in steroid signalling pathway in the brain of protandrous black porgy, Acanthopagrus schlegeli

“…To our knowledge few, if any, other data exists directly describing brain levels of endogenous E2 and testosterone in fishes. Neonatal gonadal hormone concentrations in serum and hypothalamus have been quantified in rat brain (Rhoda et al, 1984). Sexually dimorphic E2 content was observed in several brain regions of the newborn rat brain (Amateau et al, 2004).…”

Steroid hormones modulate H19 gene expression in both mammary gland and uterus

“…The H19 transcripts were only localized in some clustered cells. The large variations of H19 gene (1980); (2) Dalle et al (1978); (3) Sanyal (1978); (4) Rhoda et al (1984); (5) Smith et al (1975); (6) McCormack and Greenwald (1974); (7) Chatelain et al (1989); (8) Lesage et al (1996); (9) expression were correlated with the morphological alterations of the endometrium. A moderate expression of H19 was found in stromal cells and the myometrium during the proestrus ( Figure 3, row 4) and the level of H19 transcription increased gradually during the proliferative phase until ovulation (estrus, Figure 3, row 1).…”

Quantitative estimation of estrogen and androgen receptor-immunoreactive cells in the forebrain of neonatally estrogen-deprived male rats

“…Presumably, the sex differences in brain estrogen levels in the mPOA and Arc might represent an extremely rapid response to the hypothalamic surge in estradiol occurring in males between 0 h in utero and 1 h after delivery. 46 Since ATD treatment was not initiated until 2-4 h after birth, ATD males were most likely exposed to this hypothalamic surge in estradiol. Therefore, ATD males' brains could already have been partly organized in a male direction, i.e.…”