Brain estradiol content in newborn rats: sex differences, regional heterogeneity, and possible de novo synthesis by the female telencephalon.
Accurate assessment of gonadal steroid levels in the developing brain is critical for understanding naturally occurring steroid-mediated sexual differentiation as well as determining the physiological relevance of exogenous steroid treatments commonly used in the study of this phenomenon. Using RIA, we measured the estradiol (E(2)) content of six regions of the developing brain immediately post partum, 1 d post partum, and after injection of exogenous estradiol benzoate, testosterone propionate, or the aromatase inhibitor formestane. We found sexually dimorphic E(2) content in several regions of the newborn brain. At 2 h of life, there was significantly higher E(2) content in males vs. females in the frontal cortex, hypothalamus and preoptic area but not in the hippocampus, brainstem, or cerebellum. Surprisingly, the female hippocampus had significantly higher E(2) content than all other female regions examined. By d 1 post partum, E(2) levels had decreased precipitously in most brain regions, and only the hypothalamus maintained a sex difference. Injection of female pups with estradiol benzoate raised tissue levels to that of the male in the hypothalamus but 2- to 3-fold higher in the other five regions. Testosterone administration increased E(2) content exclusively in the preoptic area, suggesting local variation in aromatase activity and/or substrate availability. Central administration of formestane decreased estrogen content in the male cortex, hypothalamus, and preoptic area. Formestane treatment also decreased endogenous E(2) in female cortex and hippocampus, suggesting de novo synthesis selectively in these brain regions. These data corroborate and extend previous findings of sex differences in brain E(2) levels perinatally and reveal an unexpected regional heterogeneity in E(2) synthesis and/or metabolism.
Department of Physiology, University of Maryland at Baltimore, School of Medicine, 655 West Baltimore Street, Bressler RB 5020, Baltimore, Maryland 21201, USA. samat001@umaryland.edu
Stuart K
SK
Amateau
Jesse J
JJ
Alt
Carolyn L
CL
Stamps
Margaret M
MM
McCarthy
D000375:Aging / Q000378:metabolism; D000735:Androstenedione / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D047072:Aromatase Inhibitors; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000096:biosynthesis / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D013687:Telencephalon / Q000378:metabolism*; D014018:Tissue Distribution
D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors; D000735:Androstenedione; D004958:Estradiol; C014594:formestane