Dihydrotestosterone levels at midpregnancy and term: a comparison with testosterone concentrations

Six Decades of Research on Human Fetal Gonadal Steroids

Human fetal gonads acquire endocrine steroidogenic capabilities early during their differentiation. Genetic studies show that this endocrine function plays a central role in the sexually dimorphic development of the external genitalia during fetal development. When this endocrine function is dysregulated, congenital malformations and pathologies are the result. In this review, we explain how the current knowledge of steroidogenesis in human fetal gonads has benefited from both the technological advances in steroid measurements and the assembly of detailed knowledge of steroidogenesis machinery and its expression in human fetal gonads. We summarise how the conversion of radiolabelled steroid precursors, antibody-based assays, mass spectrometry, ultrastructural studies, and the in situ labelling of proteins and mRNA have all provided complementary information. In this review, our discussion goes beyond the debate on recommendations concerning the best choice between the different available technologies, and their degrees of reproducibility and sensitivity. The available technologies and techniques can be used for different purposes and, as long as all quality controls are rigorously employed, the question is how to maximise the generation of robust, reproducible data on steroid hormones and their crucial roles in human fetal development and subsequent functions.

Regulation of the epidermal growth factor receptor in fetal rat lung fibroblasts during late gestation

Lung epithelial cell differentiation is predominantly regulated by mesenchymal-epithelial cell communication. We have previously shown that epidermal growth factor (EGF) positively influences this process, and that EGF receptor (EGF-R) binding in fetal rat lung fibroblasts peaks on d18-19 of gestation, just before the onset of augmented surfactant synthesis. This regulation of EGF-R in late gestation fetal lung fibroblasts may control the timing of mesenchymal-epithelial cell communication leading to surfactant synthesis. Hormones and growth factors exert positive and negative influences on lung development, but whether they regulate the EGF-R is unknown. We hypothesized that positive [EGF, cortisol, retinoic acid (RA)] and negative [transforming growth-factor-beta1 (TGF-beta1), dihydrotestosterone (DHT)] regulators of lung cell development regulate the EGF-R in the fetal lung. We studied EGF-R binding and protein abundance in sex-specific fetal rat lung fibroblasts cultured at d17, d19, and d21. EGF-R binding was significantly elevated after RA (both sexes d17 and d19, females d21) and after DHT (females d19) treatment. EGF and cortisol had minimal or inhibitory effects on EGF-R binding. Western blot analysis showed that the observed changes in EGF-R binding were associated with similar changes in EGF-R protein. We conclude that factors that affect lung maturation continue to regulate EGF-R in a developmental, sex-specific manner during late gestation.

Stimulation of estradiol production from estrone-3-sulfate by 5 alpha-dihydrotestosterone in cultured human placental explants

The effect of androgens on the conversion of estradiol (E2) and estrone (E1) from estrone-3-sulfate (E1-S) was studied in explants of normal human term placentas. Explants incubated in medium supplemented with 2.0 microM E1-S showed that 50 microM dihydrotestosterone (DHT) stimulated E2 production 15-fold above control values after 0.5h, but neither 50 microM methyltestosterone (MT) nor 50 microM diethylstilbestrol (DES) had any effect. HCG (5.0 i.u./ml), alone or in combination with one of the androgens, did not influence the E2 production. When the explants were incubated in medium with 0.25 microM E1-S (the average concentration reported for late pregnancy plasma), DHT (0.5-50 microM) caused a dose- and time-dependent increase in E2 production, while E1 production and the combined accumulation of E2 and E1 were slightly inhibited by all doses of DHT during the 0.5-4h incubation. When E1 (0.1 microM) was used as substrate, DHT caused a dramatic dose- and time-dependent shift in the E1-E2 equilibrium towards E2. The results indicate that during late pregnancy, a particular class of androgens may increase the production of the more bioactive E2 from the circulating E1-S; the mode of action may be an enhanced conversion of E1 to E2.