Sex hormone levels in the brain of d-aspartate-treated rats

d-Aspartate (d-Asp) is an endogenous amino acid present in the central nervous system and endocrine glands of various animal taxa. d-Asp is implicated in neurotransmission, physiology of learning, and memory processes. In gonads, it plays a crucial role in sex hormone synthesis. We have investigated the effects of chronic (30 days d-Asp drinking solution) and acute (i.p. injection of 2 μmol/g bw d-Asp) treatments on sex steroid synthesis in rat brain. Furthermore, to verify the direct effect of d-Asp on neurosteroidogenic enzyme activities, brain homogenates were incubated with different substrates (cholesterol, progesterone, or testosterone) with or without the addition of d-Asp. Enzyme activities were measured by evaluating the in vitro conversion rate of (i) cholesterol to progesterone, testosterone, and 17β-estradiol, (ii) progesterone to testosterone and 17β-estradiol, (iii) testosterone to 17β-estradiol. We found that d-Asp oral administration produced an increase of approximately 40% in progesterone, 110% in testosterone, and 35% in 17β-estradiol. Similarly, the results of the acute experiment showed that at 30 min after d-Asp treatment, the progesterone, testosterone, and 17β-estradiol levels increased by 29–35%, and at 8 h they further increased by a 100% increment. In vitro experiments demonstrate that the addition of d-Asp to brain homogenate + substrate induces a significant increase in progesterone, testosterone and 17β-estradiol suggesting that the amino acid upregulates the local activity of steroidogenic enzymes.     

Gulonolactonase in the rat: influence of sex and sex hormones on development

Gulonolactonase (D(or L)-gulono-γ-lactone hydrolase, (EC 3.1.1.18) in the kidney and liver of the rat, which are known to be identical enzymes but exhibit different patterns of post-natal development. The hepatic enzyme is detectable one day after birth, increases sharply to the adult level after nine days, and shows no appreciable sex-related difference. The renal enzyme is not detectable until approximately four days after birth in the male and ten days after birth in the female. The level of renal enzyme increases slowly in both sexes until about day 27 at which time activity in the male begins to increase rapidly while it declines slowly in the female. At this time the adult male has about 20 times as much hepatic gulonolactonase as the female. Adult enzyme levels are reached at age 44 days.The normal development increase in male renal gulonolactonase is prevented by administration of 17β-estradiol but it can be restored by subsequent administration of testosterone. Testosterone alone, or in combination with glucose does not evoke precocious induction of gulonolactonase in the male, nor does it affect its level after development has begun.Of the androgens tested for their ability to induce gulonolactonase in the kidney of the adult female, the following potency was observed: 5-androstan-3α, 17β-diol > testosterone > androstandione = androstanolone. Androsterone was without effect.     

The effect of human chorionic gonadotropin on plasma steroid levels in young and old men

Seven men, 21–30 years old, and six men, 72–90 years old, were given human chorionic gonadotropin (HCG), 3,000 units a day for four days. The concentration of 17β-estradiol (1), estrone and testosterone were measured in plasma samples drawn before and during the course of HCG administration. The administration of HCG resulted in higher levels of both 17β-estradiol and testosterone in the younger as compared to the older men although the percentage increases over baseline levels were similar in both groups. HCG administration resulted in similar, absolute and relative increases of estrone in both young and old men. The levels of 17β-estradiol were higher on day 3 as compared to day 5 in young men. The relative ability to respond to exogenous gonadotropins appears to be preserved despite ageing and loss of libido and potentia. The absolute response is, however, somewhat less in old men as compared to young.     

17β-Estradiol protects against acetaminophen-overdose-induced acute oxidative hepatic damage and increases the survival rate in mice

Acetaminophen overdose causes acute liver injury or even death in both humans and experimental animals. We investigated the effect of 17β-estradiol against acetaminophen-induced acute liver injury and mortality in mice. Male mice were given acetaminophen (p-acetamidophenol; 300 mg/kg; orally) to induce acute liver injury. Acetaminophen significantly increased the levels of aspartate transaminase, alanine transaminase, myeloperoxidase, lipid peroxidation, and glutathione reductase, but it decreased superoxide dismutase, catalase, and glutathione. In addition, acetaminophen-induced mortality began 4h post-treatment, and all mice died within 9h. 17β-Estradiol (200 μg/kg; i.p.) protected against acetaminophen-induced oxidative hepatic damage by inhibiting neutrophil infiltration and stimulating the antioxidant defense system. However, 17β-estradiol did not affect acetaminophen-induced glutathione depletion or increased glutathione reductase activity. We conclude that 17β-estradiol specifically attenuates acute hepatic damage and decreases mortality in acetaminophen-overdosed male mice.     

Acute estrogen treatment facilitates recognition memory consolidation and alters monoamine levels in memory-related brain areas

Acute effects of estrogens on mnemonic processes were examined at the behavioral and neurochemical levels. 17β-estradiol and 17α-estradiol influences on memory consolidation were assessed using object placement (OP) and object recognition (OR) tasks. Subjects received treatment immediately after a sample trial (exploring two novel objects), and memory of objects (OR memory) or location of objects (OP memory) was tested 4 h later. Both isomers of estradiol enhanced memory. For spatial memory, 15 and 20 µg/kg of 17β-estradiol facilitated OP, while lower and higher doses were ineffective. 17α-estradiol had a similar pattern, but a lower dose was effective. When treatment was delayed until 45 min after a sample trial, memory was not enhanced. For non-spatial memory, OR was facilitated at 5 µg/kg of 17β-estradiol and at 1 and 2 µg/kg of 17α-estradiol and, similar to OP, lower and higher doses were ineffective. These data demonstrate that beneficial effects of estrogens are dose, time and task dependent, and the dose-response pattern is an inverted U. Because monoamines are known to have contributions to memory, brains were removed 30 min after treatment for measurements of dopamine (DA), norepinephrine (NE), serotonin (5-HT), and metabolites. Estrogen elevated 5HT, NE metabolite MHPG, turnover ratio of NE to MHPG, and DA metabolite DOPAC levels in the prefrontal cortex, while NE and MHPG were decreased in the hippocampus. Thus, acute estrogens exert rapid effects on memory consolidation and neural function, which suggests that its mnemonic effects may involve activation of membrane associated estrogen receptors and subsequent signaling cascades, and that monoamines may contribute to this process.     

Sex-specific effects of estrogen and androgen on gene expression in human monocyte-derived osteoclasts

Estrogen and androgen are both critical for the maintenance of bone, but the target cells, mechanisms, and responses could be sex-specific. To compare sex-specific actions of estrogen and androgen on osteoclasts, human peripheral blood mononuclear precursor cells from adult Caucasian males (n = 3) and females (n = 3) were differentiated into osteoclasts and then treated for 24 h with 17β-estradiol (10 nM) or testosterone (10 nM). Gene expression was studied with a custom designed qPCR-based array containing 94 target genes related to bone and hormone action. In untreated osteoclasts, 4 genes showed significant gender differences. 17β-estradiol significantly affected 12 genes in osteoclasts from females and 6 genes in osteoclasts from males. Fifteen of the 18 17β-estradiol-responsive genes were different in the cells from the two sexes; 2 genes affected by 17β-estradiol in both sexes were regulated oppositely in the two sexes. Testosterone significantly affected 6 genes in osteoclasts from females and 2 genes in osteoclasts from males; all except one were different in the two sexes. 17β-estradiol and testosterone largely affected different genes, suggesting that conversion of testosterone to 17β-estradiol had a limited role in the responses. The findings indicate that although osteoclasts from both sexes respond to 17β-estradiol and testosterone, the effects of both 17β-estradiol and testosterone differ in the two sexes, highlighting the importance of considering gender in the design of therapy.     

Cellular and molecular mechanisms of 17β-estradiol postconditioning protection against gastric mucosal injury induced by ischemia/reperfusion in rats

AimsTo investigate the protective effects of 17β-estradiol postconditioning against ischemia/reperfusion (I–R)-induced gastric mucosal injury in rats.Main methodsThe animal model of gastric ischemia/reperfusion was established by clamping of the celiac artery for 30 min and reperfusion for 30 min, 1 h, 3 h, 6 h, 12 h or 24 h. 17β-estradiol at doses of 5, 50 or 100 μg/kg (rat) was administered via peripheral veins 2 min before reperfusion. In a subgroup of rats, the estrogen receptor antagonist fulvestrant (Ful, 2 mg/kg) was intravenously injected prior to 17β-estradiol administration. Histological and immunohistochemical methods were employed to assess the gastric mucosal injury index and gastric mucosal cell apoptosis and proliferation. The malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity, xanthine oxidase (XOD) activity and hydroxyl free radical (–OH) inhibitory ability were determined by colorimetric assays. Subsequently, the expression of Bcl-2 and Bax in rat gastric mucosa was examined by western blotting.Key findings17β-estradiol dose-dependently inhibited gastric I–R (GI–R) injury, and 17β-estradiol (50 μg/kg) markedly attenuated GI–R injury 1 h after reperfusion. 17β-estradiol inhibited gastric mucosal cell apoptosis and promoted gastric mucosal cell proliferation in addition to increasing SOD activity and –OH inhibitory ability and decreasing the MDA content and XOD activity. The Bax protein level increased 1 h after GI–R and was markedly reduced by intravenous administration of 17β-estradiol. In contrast, the level of Bcl-2 protein decreased 1 h after GI–R and was restored to normal levels by intravenous administration of 17β-estradiol. These effects of 17β-estradiol were inhibited by pretreatment with fulvestrant.Significance17β-estradiol postconditioning should be investigated further as a possible strategy against gastric mucosal injury.     

A single injection of 17 beta-estradiol facilitates sexual behavior in castrated male mice

Sexual behavior was assessed in castrated adult CD-1 male mice given exogenous steroids under various treatment regimens. Castrated mice maintained on 20 μg testosterone (T) daily for 1 week, but given 250 μg testosterone propionate (TP) on the day of testing showed higher levels of copulatory activity than intact mice or the males receiving an additional dose of 20 μg T on the test day, although plasma testosterone levels were not different at the time of behavioral testing. Castrated males given 50, 125, or 250 μg TP for 1 week including the day of testing showed higher levels of sexual behavior than males receiving the same doses of TP only once, on the test day. A single injection of 17β-estradiol (E₂) completely restored the male copulatory pattern, including ejaculation, in castrated mice under every condition examined. Testosterone and dihydrotestosterone (DHT) were less effective than E₂, as was the combination of E₂ and DHT. The relative efficacy of a single dose of T, DHT, and E₂ plus DHT was dependent upon factors such as the delay between steroid administration and testing, as well as whether or not the castrated mice received androgen replacement prior to testing. Estradiol benzoate (E₂B) was not capable of restoring sexual behavior in castrated mice in this study. The comparison of results obtained with TP, T, E₂, and E₂B suggests that an appreciable, but not necessarily sustained, elevation of E₂ levels in the brain may be critical in the facilitation of male copulatory behavior in mice.     

Effect of androstenedione on the growth and meiotic competence of bovine oocytes from early antral follicles

Summary Medium that contains 17β-estradiol has been reported to support in vitro growth of bovine oocytes, isolated from early antral follicles, until the final stage. The aim of this study was to determine the effects of androstenedione in medium on such growing bovine oocytes. Oocyte-granulosa cell complexes were collected from early antral follicles and cultured for 14 days in medium supplemented with 17β-estradiol (0, 10 and 100 ng/ml) or androstenedione (0, 10 and 100 ng/ml). The mean diameter of oocytes measured after seeding on the culture substrate was 96.9 μm (n = 191). Either steroid was necessary for maintainance of the organization of oocyte-granulosa cell complexes over the 14-day culture period. In the 17β-estradiol- or the androstenedione-supplemented medium about 80% or 65%, respectively, of viable oocytes were recovered. In both groups the increase in oocyte size was significant after 14 days. The in vitro grown oocytes were cultured for a further 22-24 h for oocyte maturation; 13% and 30% of oocytes grown in the 10 and 100 ng/ml 17β-estradiol-supplemented medium reached metaphase II, respectively; more than 64% of oocytes grown in the androstenedione-supplemented medium matured to metaphase II. These results show that androstenedione, as 17β-estradiol, can maintain the viability of bovine oocyte-granulosa cell complexes and support the growth of oocytes, and that androstenedione promotes the acquisition of oocyte meiotic competence efficiently at a low dose.     

Increase of myometrial activity correlated with variations in 17β-estradiol and progesterone uterine concentrations in mid-term pregnant rat: estrogen agonist effect of 4-hydroxytamoxifen

The objective of this investigation was to examine the effects of 4-hydroxytamoxifen on the uterine activity. For this, we evaluated the electrical activity of the myometrium, chronically, in conscious unrestrained rats at mid-pregnancy. We also examined the tissular progesterone and 17β-estradiol concentrations in the myometrium and uterus 6 hours after administration of 4-hydroxytamoxifen. Comparison of myometrial electrical activities recorded during the control period with those obtained during the two periods (6 and 24 hours) after administration of4-hydroxytamoxifen (80 μg.kg⁻¹, s.c.) showed an increase in simultaneity of uterine contractions (P < 0.01). Tissular steroid hormone measurement by radioimmunoassay shows a fall of progesterone in the myometrium (P < 0.001) and of 17β-estradiol in the uterus (P < 0.01), 6 hours after administration of 4-hydroxytamoxifen. In the myometrium, for 50% of animals, 17β-estradiol concentration decreased (P < 0.01) and for 50% of animals it increased (P < 0.05). The decrease in progesterone is significant in the myometrium and in the whole uterus (respectively P < 0.001 and P < 0.01), 24 hours after administration of 4-hydroxytamoxifen. The 17β-estradiol concentration significantly decreased for all animals in the myometrium (P < 0.01) and in the uterus (P < 0.01), after this time. It appears that variation in progesterone induces the activation of uterine motility and exerts an effect on some factors involved in the regulation of the rat myometrium at mid-pregnancy.     

Pro-survival effects of 17β-estradiol on osteocytes are mediated by nitric oxide/cGMP via differential actions of cGMP-dependent protein kinases I and II

Estrogens promote bone health in part by increasing osteocyte survival, an effect that requires activation of the protein kinases Akt and ERK1/2, but the molecular mechanisms involved are only partly understood. Because estrogens increase nitric oxide (NO) synthesis and NO can have anti-apoptotic effects, we examined the role of NO/cGMP signaling in estrogen regulation of osteocyte survival. Etoposide-induced death of MLO-Y4 osteocyte-like cells, assessed by trypan blue staining, caspase-3 cleavage, and TUNEL assays, was completely prevented when cells were pre-treated with 17β-estradiol. This protective effect was mimicked when cells were pre-treated with a membrane-permeable cGMP analog and blocked by pharmacological inhibitors of NO synthase, soluble guanylate cyclase, or cGMP-dependent protein kinases (PKGs), supporting a requirement for NO/cGMP/PKG signaling downstream of 17β-estradiol. siRNA-mediated knockdown and viral reconstitution of individual PKG isoforms demonstrated that the anti-apoptotic effects of estradiol and cGMP were mediated by PKG Iα and PKG II. Akt and ERK1/2 activation by 17β-estradiol required PKG II, and cGMP mimicked the effects of estradiol on Akt and ERK, including induction of ERK nuclear translocation. cGMP induced BAD phosphorylation on several sites, and experiments with phosphorylation-deficient BAD mutants demonstrated that the anti-apoptotic effects of cGMP and 17β-estradiol required BAD phosphorylation on Ser(136) and Ser(155); these sites were targeted by Akt and PKG I, respectively, and regulate BAD interaction with Bcl-2. In conclusion, 17β-estradiol protects osteocytes against apoptosis by activating the NO/cGMP/PKG cascade; PKG II is required for estradiol-induced activation of ERK and Akt, and PKG Iα contributes to pro-survival signaling by directly phosphorylating BAD.     

Tissue selectivity and potential clinical applications of trenbolone (17β-hydroxyestra-4,9,11-trien-3-one): A potent anabolic steroid with reduced androgenic and estrogenic activity

Recently, the development of selective androgen receptor modulators (SARMs) has been suggested as a means of combating the deleterious catabolic effects of hypogonadism, especially in skeletal muscle and bone, without inducing the undesirable androgenic effects (e.g., prostate enlargement and polycythemia) associated with testosterone administration. 17β-Hydroxyestra-4,9,11-trien-3-one (trenbolone; 17β-TBOH), a synthetic analog of testosterone, may be capable of inducing SARM-like effects as it binds to androgen receptors (ARs) with approximately three times the affinity of testosterone and has been shown to augment skeletal muscle mass and bone growth and reduce adiposity in a variety of mammalian species. In addition to its direct actions through ARs, 17β-TBOH may also exert anabolic effects by altering the action of endogenous growth factors or inhibiting the action of glucocorticoids. Compared to testosterone, 17β-TBOH appears to induce less growth in androgen-sensitive organs which highly express the 5α reductase enzyme (e.g., prostate tissue and accessory sex organs). The reduced androgenic effects result from the fact that 17β-TBOH is metabolized to less potent androgens in vivo; while testosterone undergoes tissue-specific biotransformation to more potent steroids, dihydrotestosterone and 17β-estradiol, via the 5α-reductase and aromatase enzymes, respectively. Thus the metabolism of 17β-TBOH provides a basis for future research evaluating its safety and efficacy as a means of combating muscle and bone wasting conditions, obesity, and/or androgen insensitivity syndromes in humans, similar to that of other SARMs which are currently in development.     

The stimulatory effect of testosterone propionate and 17β-estradiol on 5′-methylthioadenosine phosphorylase activity in rat target tissues

The effect of castration and subsequent administration of 17β-estradiol and testosterone propionate on 5′-methylthioadenosine phosphorylase activity in rat target tissues was studied. Castration 34 days earlier resulted in a 95 reduction in ventral prostate 5′-methylthioadenosine phosphorylase activity and 16 days earlier in a 67% reduction in uterine 5′-methylthiodenosine phosphorylase activity. Four days of testosterone propionate administration stimulated ventral prostate 5′-methylhioadenosine phosphorylase activity 32% above castrate levels, which represented more than 50% of the intact control levels. 17β-Estradiol on the other hand stimulated uterine 5′-methylthioadenosine phosphorylase activity of 35% above castrate controls within 24h and with 3 days of continuous hormone treatment to within 97% of the intact control levels. However, castration and subsequent 17β-estradiol administration did not affect 5′-methylthioadenosine phosphorylase activity in rat liver and lung. Both prostate and uterine 5′-methylthioadenosine phosphorylase were shown to metabolize 5′-methylthioadenosine to 5′-methylthioribose through a 5′-methythiribose 1-phosphate intermediate. The data suggest that 5′-methylthioadenosine is not allowed to accumulate in rat target tissues even under conditions which are known to stimulate polyamine synthesis.     

Selective retention of oestradiol by cell nuclei in specific brain regions of the ovariectomized rat

—Cell nuclei were isolated from four regions of the brains of ovariectomized female rats 2 hr after the injection of [³H]oestradiol. By light microscopy, the nuclear pellets contained highly purified nuclei of neuronal and glial cells with little cytoplasmic contamination. Tritium was concentrated in cell nuclei from the preoptic-hypothalamic area, to a lesser extent in nuclei from the amygdaloid region and hippocampus, and least of all in cerebral cortical nuclei. In comparison with whole homogenates (= 1-0), the nuclear concentrations of radioactivity were 12·9, 4·7, 1·9 and 0·8, respectively. Approximately 40 per cent of the radioactivity in homogenates of the preoptic-hypothalamic area was present in cell nuclei, and upon TLC more than 85 per cent of the radioactive material in the nuclei exhibited the R_F of oestradiol-17β. Pretreatment of ovariectomized females with 1 mg of unlabelled oestradiol 30 min before the injection of labelled hormone abolished the nuclear uptake of [³H]oestradiol in all four regions of the brain. A concurrent injection of 10 μg of unlabelled oestradiol-17β significantly reduced nuclear uptake, while a similar injection of testosterone or oestradiol-17α had no significant effect. One mg of oestradiol-17α, but not testosterone, did reduce nuclear uptake. The retention of [³H]oestradiol by the preoptic-hypothalamic area decreased exponentially in the tissue from 30 min to 4 h after an intraperitoneal injection; however, nuclear binding reached a peak at 1-2 h and still showed high retention at 4 h. These results, together with observations in other laboratories of morphological changes induced by oestrogens, establish that certain regions of the brain are bona fide targets for the action of oestradiol.     

Estrogen alleviates neuropathic pain induced after spinal cord injury by inhibiting microglia and astrocyte activation

Neuropathic pain after spinal cord injury (SCI) is developed in about 80% of SCI patients and there is no efficient therapeutic drug to alleviate SCI-induced neuropathic pain. Here we examined the effect of estrogen on SCI-induced neuropathic pain at below-level and its effect on neuroinflammation as underlying mechanisms. Neuropathic pain is developed at late phase after SCI and a single dose of 17β-estradiol (100, 300?μg/kg) were administered to rats with neuropathic pain after SCI through intravenous injection. As results, both mechanical allodynia and thermal hyperalgesia were significantly reduced by 17β-estradiol compared to vehicle control. Both microglia and astrocyte activation in the lamina I and II of L4-5 dorsal horn was also inhibited by 17β-estradiol. In addition, the levels of p-p38MAPK and p-ERK known to be activated in microglia and p-JNK known to be activated in astrocyte were significantly decreased by 17β-estradiol. Furthermore, the mRNA expression of inflammatory mediators such as Il-1β, Il-6, iNos, and Cox-2 was more attenuated in 17β-estradiol-treated group than in vehicle-treated group. Particularly, we found that the analgesic effect by 17β-estradiol was mediated via estrogen receptors, which are expressed in dorsal horn neurons. These results suggest that 17β-estradiol may attenuate SCI-induced neuropathic pain by inhibiting microglia and astrocyte activation followed inflammation.     

(3H)-estradiol binding by chick liver nuclear extracts: mechanism of increase in binding following estradiol injection.

Specific high affinity binding of [3H]-estradiol by 0.5 M KCl extracts of chick liver nuclei is substantially increased by estradiol injection of the immature chick. The effect is observed shortly after estradiol injection, while the estradiol-induced production of serum phosphoproteins (vitellogenic response) is not detectable until about 24 hr. Cycloheximide given 90 min before estradiol inhibits the increase in nuclear binding for 12-15 hr. At 24-48 hr the levels of nuclear binding are similar to those in the estradiol-treated animals not given cycloheximide, but serum phosphoprotein levels are depressed by about 80% at 48 hr. By 75 hr however the serum of the cycloheximide-treated estrogenized chicks contains about twice as much phosphoprotein as does serum of chicks given estradiol alone. It is suggested that the inhibition of protein synthesis for 12-15 hr delays the vitellogenic response until sufficient levels of nuclear [3H]-estradiol binding protein can be synthesized. A correlation between the levels of nuclear [3H]-estradiol binding at 24 hr and phosphoprotein at 48 hr is shown in a dose-response experiment. In vitro, nafoxidine-HCl (Upjohn 11,100 A) inhibits binding of [3H]-estradiol by the chick liver nuclear extracts. In vivo, a single injection of nafoxidine with estradiol inhibits phosphoprotein production. Injection of nafoxidine alone results in a small but significant increase in [3H]-estradiol binding by nuclear extracts, but it is not estrogenic. A possible interpretation is that nafoxidine transfers low levels of a putative cytosol receptor to the nucleus, but is unable to induce the amplification mechanism required to give the levels of nuclear estradiol-binding protein needed for the vitellogenic response.     

Estradiol-mediated suppression of CYP1B1 expression in mouse MA-10 Leydig cells is independent of protein kinase A and estrogen receptor

Estrogens have multifaceted roles in mammalian testis. In the present study, we focused on estradiol as a potential regulator of testicular cytochrome P450 1B1 (CYP1B1) expression and investigated the possible mechanisms involved in the estradiol-mediated suppression. CYP1B1 protein levels were measured in the testes of rats that were treated with 17β-estradiol benzoate (1.5 mg/kg) at different stages of development. In addition, CYP1B1 mRNA levels were measured in mouse MA-10 Leydig tumor cells treated with (a) various concentrations of 17β-estradiol benzoate, (b) 17β-estradiol benzoate in the presence of exogenous luteinizing hormone (LH), or (c) 17β-estradiol benzoate in the presence of ICI 182,780, a competitive steroidal antagonist of estrogen receptors (ERs). Treatment of neonatal, pubertal, or adult rats with 17β-estradiol benzoate was associated with a reduction of approximately 90% in testicular CYP1B1 protein content compared to age-matched controls. Treatment of MA-10 cells with 17β-estradiol benzoate (10-500 nM) produced a concentration- and time-dependent decrease in CYP1B1 mRNA levels, but had no effect on LH receptor mRNA levels or on protein kinase A (PKA) activity. However, 17β-estradiol benzoate (10-500 nM), regardless of the concentration tested, failed to attenuate the LH-elicited increase in CYP1B1 mRNA or PKA activity in MA-10 cells that were co-treated with LH and estradiol. Similarly, ICI 182,780 (10-1000 μM) did not reverse the suppressive effect of estradiol on CYP1B1 mRNA expression in MA-10 cells co-treated with estradiol and ICI 182,780. The results indicate that downregulation of testicular CYP1B1 by estradiol was independent of PKA activity and was not mediated by ERs in MA-10 cells.     

A comparative study of the effect of 17β-estradiol and estriol on peripheral pain behavior in rats

Although estradiol has been reported to influence pain sensitivity, the role of estriol (an estradiol metabolite and another widely used female sex hormone) remains unclear. In this study, pain behavior tests, whole-cell patch clamp recording and Western blotting were used to determine whether estriol plays a role in pain signal transduction and transmission. Either systemic or local administration of 17β-estradiol produced a significant rise of mechanical pain threshold, while estriol lacked this effect in normal and ovariectomized (OVX) rats following estriol replacement. Local administration of 17β-estradiol or estriol significantly decreased ATP-induced spontaneous hind-paw withdrawal duration (PWD), which was blocked by an estrogen receptor antagonist, ICI 182, 780. However, systemic application of estriol in normal or OVX rats lacked this similar effect. In cultured dorsal root ganglion neurons, estriol attenuated α,β-methylene ATP-induced transient currents which were blocked by ICI 182, 780. In complete Freund's adjuvant treated (CFA) rats, systemic application of 17β-estradiol or estriol decreased the mechanical pain threshold significantly, but did not change the inflammatory process. Similar effects were observed after estriol replacement in OVX rats. The expression of c-fos in lumbosacral spinal cord dorsal horn (SCDH) was increased significantly by administration of 17β-estradiol but not estriol, and not by estriol replacement in OVX rats. These results suggest that 17β-estradiol but not estriol plays an anti-hyperalgesic role in physiological pain. However, both peripheral 17β-estradiol and estriol play anti-hyperalgesic roles in ATP-induced inflammatory pain. Systemic application of estriol as well as 17β-estradiol plays hyperalgesic roles in CFA-induced chronic pain.     

Plasma profiles of the sex steroids and gonadotropins in maturing female spring chinook salmon (Oncorhynchus tshawytscha)

Plasma testosterone concentrations were low through the spring and early summer, concentrations began rising in late July and reached maximum levels by ovulation in September. Plasma concentrations of 11-ketotestosterone were low throughout sexual maturation until ovulation when a significant increase occurred. Plasma androstendione and 17β-estradiol concentrations were high throughout sexual maturation, and decreased significantly at ovulation. Plasma 17α,20β-dihydroxy-4-pregnen-3-one concentrations were low throughout maturation, and increased significantly at ovulation. Plasma gonadotropin I concentrations paralleled those of estradiol and exceeded gonadotropin II levels prior to ovulation. Plasma concentrations of gonadotropin II were low throughout the spring and summer, increasing dramatically at ovulation.     

Regulation of reproduction- and biomarker-related gene expression by sex steroids in the livers and ovaries of adult female western mosquitofish (Gambusia affinis)

To assess the adverse toxicological effects of steroid hormones on western mosquitofish (Gambusia affinis), 180 adult females were exposed to individual or binary combinations of progesterone (1μg/L), testosterone (1μg/L) and 17β-estradiol (1μg/L) for eight days. The expression patterns of vitellogenin, estrogen receptor, androgen receptor, metallothionein, and cytochrome P450 1A genes in mosquitofish varied according to tissue as well as the specificity of steroids. Treatment by progesterone or testosterone alone inhibited target gene expression in the livers. The expression levels of both vitellogenin A and vitellogenin B mRNAs were up-regulated by17β-estradiol, and a parallel induction of estrogen receptor α mRNA expression was also observed in the livers. In addition, 17β-estradiol treatment alone suppressed androgen receptor α, metallothionein and cytochrome P450 1A mRNA expression in the livers. In general, multiple hormone treatments had different effects on target gene expression compared with corresponding hormone alone. The results demonstrate that steroid hormones cause multiple biological responses including the expression of vitellogenin, estrogen receptor and androgen receptor mRNA in the hormone signaling pathways and the expression of metallothionein and cytochrome P450 1A mRNA in the xenobiotic signaling pathway.