Subcellular action of estradiol-17 beta in a freshwater prawn Macrobrachium rosenbergii

Effects of estradiol and progesterone on the reproduction of the freshwater crayfish Cherax albidus

In this study we have investigated the role of 17beta-estradiol and progesterone in the reproduction of the crayfish Cherax albidus by using vitellogenin (VTG) as a biomarker. Early-vitellogenic (EV), full-vitellogenic (FV), and non-vitellogenic (NV) females of Cherax albidus were treated with 17beta-estradiol, progesterone, or both for 4 weeks. Levels of VTG mRNA in the hepatopancreas were detected by RT-PCR. The PCR product was sequenced and showed 97% homology with Cherax quadricarinatus VTG. 17beta-estradiol was more effective than progesterone and 17beta-estradiol plus progesterone in increasing the vitellogenin transcript in the hepatopancreas of EV and FV females. On the contrary, progesterone was more effective than 17beta-estradiol and 17beta-estradiol plus progesterone in increasing the vitellogenin concentration in the hemolymph of EV and FV females. Hepatopancreas histology and fatty acid composition of females injected with hormones showed major modifications. No effects were registered in NV females. In conclusion, 17beta-estradiol and progesterone influence VTG synthesis, although our data indicate that they act through different pathways and are not effective until the proper hormonal environment is established, as demonstrated by their inefficacy in NV females.

Effects of 17 beta-estradiol on the vitellogenin synthesis and oocyte development in the ovary of kuruma prawn (Marsupenaeus japonicus)

The effects of 17 beta-estradiol on induction of vitellogenin synthesis and oocyte development were investigated in previtellogenic ovary of immature kuruma prawn (Marsupenaeus japonicus) incubated with Medium 199. After three days incubation of previtellogenic ovary, Vg concentrations in media containing 3.6 nM, 36.7 nM, 367 nm and 3671 nM 17 beta-estradiol were significantly (p<0.01) greater than that of Ringer solution or the pure ethanol vehicle. Furthermore, a more advanced stage of oocyte development at oil globule stage (primary vitellogenic stage), which is surrounded by round and greatly expanded follicle cells, was observed in previtellogenic ovarian pieces incubated in media containing 3.6, 36.7, 367 and 3671 nM 17 beta-estradiol. The results of these studies show that 17 beta-estradiol induces Vg synthesis and appearance of primary vitellogenic oocyte in the ovary of immature prawns.

Steroid estrogens in ocean sediments

This paper gives results from a study measuring the abundance of steroid hormones in ocean sediments in the proximity of a deep ocean sewage outfall. The outfall is discharge point for an enhanced primary sewage treatment plant and sediment samples were taken adjacent and 7 km from the outfall. All samples contained steroid estrogens at nanogram per gram levels with higher concentrations at the 7 km sampling site. The concentration of estrone ranged from (0.16-1.17 ng/g), 17beta-estradiol (0.22-2.48 ng/g) and the synthetic 17alpha-ethinylestradiol (<0.05-0.5 ng/g). The values detected correspond with estimates based on the proportion of estrogens sorbed to particles in the effluent and the expected proportion of particles originating from sewage in the ocean sediments. The results suggest that estrogens associated with the particulate fraction aggregate on contact with high ionic strength seawater and settle to the seafloor after discharge through deep ocean outfalls.

Metabolism of estrogens and androgens by scleractinian corals

Estrogens and androgens are steroids that act as reproductive hormones in vertebrates. These compounds have also been detected in reef-building corals and other invertebrates, where they are hypothesized to act as bioregulatory molecules. Experiments were conducted using labeled steroid substrates to evaluate metabolism of estrogens and androgens by coral homogenates. GC-MS analysis of 13C-labeled steroids showed that Montipora capitata coral homogenates or fragments could convert estradiol to estrone and testosterone to androstenedione and androstanedione, evidence that M. capitata contains 17beta-hydroxysteroid dehydrogenase and 5alpha-reductase. When homogenates from three coral species and symbiotic dinoflagellates (zooxanthellae) were incubated with tritiated steroid substrates, metabolites separated by thin-layer chromatography confirmed that 17beta-hydroxysteroid dehydrogenase activity occurred in all species tested. NADP+ was the preferred cofactor in dehydrogenation reactions with coral homogenates. Reduction of estrone and androstenedione occurred at lower rates and aromatization of androgens was not observed. It is unclear whether estrogens detected previously in coral tissues are produced endogenously or sequestered in coral tissue from dietary or environmental sources. Previous studies have demonstrated that corals can take up estrogens from the water column overlying coral reefs. Considered in total, these observations suggest corals could alter the concentration or form of steroids available to reef organisms.

Gene expression profile in the livers of rats orally administered ethinylestradiol for 28 days using a microarray technique

To identify genes showing responses to estrogen exposure in the livers of animals in a repeated oral dose toxicity study, dose-dependent gene expression profiles were analyzed using high-density oligonucleotide microarrays in Sprague-Dawley rats of both sexes administered ethinylestradiol (EE) for 28 days at concentrations of 0, 0.01, 0.1, and 1.0 ppm in the diet. Among 3776 genes examined, examples showing increased expression on EE-treatment were detected predominantly in females. Genes showing dose-dependent up-regulation with greater than five-fold change at 1.0 ppm from the control levels were found to, respectively, number 4 in males, and 24 in females. Most of the latter exhibited relatively high basal expression as well as low variability, and many exhibited clear dose-dependence. Genes showing dose-dependent down-regulation were rather few, and many of those affected exhibited relatively low expression levels with large variation between animals, like genes showing dose-unrelated expression patterns in both sexes or dose-dependent up-regulation in males. Considering that detection of changes in endocrine-linked organs and estrous cyclicity is only possible at the high dose of 1.0 ppm, up-regulation of genes dose-dependently in females provides a sensitive tool to detect estrogenic effects in the rat liver in the framework of the 28-day toxicity study.

Immunological evidence for progesterone and estradiol receptors in the freshwater crayfish Austropotamobius pallipes

In this article, we present evidence for progesterone and estradiol receptors (PR and ER, respectively) in the female of the crayfish Austropotamobius pallipes. To our knowledge, this is the first report of sex steroid receptors in crustaceans. By using immunohistochemistry and Western blotting approaches and employing three different antibodies against PR (human PR, chicken PR-hinge region, and chicken PR A/B domain) and antibodies against human ER, we showed the presence of PR in the ovary and hepatopancreas and ER in the hepatopancreas of the freshwater crayfish A. pallipes. The immunological characteristics and the tissue localization suggest a relatedness with both PR and ER in vertebrates along with their involvement in the modulation of reproductive functions in this crustaceans.

A parameter for detecting estrogenic exposure in the copepod Acartia tonsa

Literature on the basic endocrinology of crustaceans, such as crab, lobster and shrimp, suggest that estrogens, e.g., 17beta-estradiol, are stimulating hormones in female sexual maturation and egg production in crustaceans. The copepod Acartia tonsa, has continuous egg production. A profile of the egg production per time unit through the maturation of this species may be used as an expression of the degree of maturation of the female internal reproductive organs. Comparison of control profiles with profiles of estrogen-exposed copepods may thus demonstrate that estrogen exposure results in a steeper maturation profile. The proposed endpoint was identified by exposing copepods to the natural estrogen 17beta-estradiol and the antropogenic estrogen bisphenol A. Both compounds produced significant effects at 23 and 20 microg/L, respectively. Since bisphenol A is traditionally believed to be less estrogenic than 17beta-estradiol, the nonestrogen 2, 3-dichlorophenole was tested at 13.6 microg/L (molar concentration equal to 23 microg/L 17beta-estradiol) to test if the response is a general nonestrogenic toxic stress effect. The 2,3-dichlorophenole produced no effect.

Methoxychlor stimulates estrogen-responsive messenger ribonucleic acids in mouse uterus through a non-estrogen receptor (non-ER) alpha and non-ER beta mechanism

This study examined the effects of the xenoestrogen methoxychlor (Mxc) on messenger RNA (mRNA) concentrations of two estrogen-responsive uterine genes, lactoferrin (LF) and glucose-6-phosphate dehydrogenase (G6PD). Ovariectomized wild-type (WT) and estrogen receptor (ER) alpha-knockout (ER alphaKO) mice were treated with Mxc or estradiol-17beta (E2) to determine whether Mxc acts via pathways that involve ER alpha. In WT mice, both E2 and Mxc stimulated increases in uterine LF and G6PD mRNA concentrations in a dose-dependent manner. Competitive pretreatment with the pure antiestrogen ICI 182,780 dramatically reduced E2-stimulated increases in mRNA concentrations but had no effect on Mxc-induced effects. Competitive pretreatment with E2 had only a partially inhibitory effect on Mxc-induced responses. In the ER alphaKO mouse, E2 had little effect on uterine LF or G6PD mRNA concentrations, whereas Mxc stimulated marked increases in both LF and G6PD mRNAs. The Mxc-induced increases in LF and G6PD mRNAs in the ER alphaKO mouse were not suppressed by competitive pretreatment with either E2 or ICI 182,780. Fold increases in mRNA concentrations for both genes induced by Mxc were similar for WT and ER alphaKO mice. The results surprisingly indicate that a xenoestrogen, Mxc, can increase LF and G6PD mRNA concentrations by a mechanism that is not mediated through ER alpha or ER beta, and acts through another pathway.

Estrogen as a neuromodulator of MPTP-induced neurotoxicity: effects upon striatal dopamine release

The effects of estrogen upon MPTP-induced neurotoxicity were examined using in vitro superfusion. In Experiment 1, striatal tissue from ovariectomized rats was infused with MPP+ (10 microM), a combination of MPP+ and 17beta-estradiol (300 nM), the same dose of estradiol preceding MPP+, or no treatment infusion. The effects of these treatments on dopamine release rates during the infusion periods were determined. Infusion of MPP+ resulted in a significant increase in dopamine release as compared to the control. Estradiol added to the MPP+ infusion significantly attenuated this dopamine (DA) release, while estradiol treatment preceding the MPP+ had no effect. In Experiment 2, three different doses of estradiol (0.3, 3, or 300 nM) were infused simultaneously with the MPP+. Doses of estradiol below 300 nM did not attenuate the DA release. In Experiment 3, estradiol alone (300 nM) was infused, to determine dopamine release rate effects of the hormone itself. There was no difference between estradiol treated and non-infused control groups. These results demonstrate that the gonadal steroid hormone estradiol can modulate responses of striatal dopamine neurons to MPP+ by altering the immediate increase in dopamine release which occurs in response to this neurotoxin. These modulating effects of estradiol are dose-dependent, and represent a direct effect upon striatal neurons, most likely involving a non-genomic mechanism of action. These results implicate that hormonal modulation of nigrostriatal dopaminergic neurotoxicity may represent an important variable responsible for the sex differences which are reported in Parkinson's disease.

Estrogen as a neuroprotectant against MPTP-induced neurotoxicity in C57/B1 mice

Castrated retired breeder male and female mice were treated or not with a 17 beta-estradiol pellet. At 10 days postcastration +/- estrogen treatment all animals were treated with MPTP. Five days later, concentrations of dopamine were determined from the corpus striatum and olfactory tubercle. Both castrated male and female mice treated with estrogen had significantly greater concentrations of dopamine within the corpus striatum compared with their respective gender controls, which did not receive estrogen. By contrast, no statistically significant differences in olfactory tubercle dopamine concentrations were obtained. Overall concentrations of dopamine within the corpus striatum, but not olfactory tubercle, were substantially greater in female vs. male mice. These data demonstrate that treatment with estrogen prevents reductions in corpus striatal dopamine concentrations in castrated mice treated with MPTP. Interestingly, this effect of estrogen was observed in both male and female mice. These results suggest that estrogen may serve as a neuroprotectant against an agent that is toxic to the nigrostriatal dopaminergic system in both male and female animal models of Parkinsonism.