Estrogen sulfatase and steroid sulfatase activities in intrauterine tissues of the pregnant guinea pig

The possible role of intrauterine estrogen sulfatase and steroid sulfatase around the time of parturition in the guinea pig was investigated. [3H]Estrone sulfate or [3H]pregnenolone sulfate was incubated with intrauterine tissues. Estrogen sulfatase was found in placenta, endometrium, decidua basalis, amnion and chorion. The presence of steroid sulfatase was established in endometrium and decidua basalis but not in placenta or the fetal membranes. Examination of activities in early (days 32-35), mid (days 44-46) and late (within 5 days of parturition) gestation revealed no significant change in estrogen sulfatase specific activity in decidua basalis. However, in chorion and endometrium this activity was seen to increase approx. 12-fold (P less than 0.001) and 2.8-fold (P less than 0.001), respectively, from early to late gestation. In placenta, estrogen sulfatase activity appeared to increase 2.4-fold (P less than 0.001) and in amnion it decreased 2.8-fold (P less than 0.002). Steroid sulfatase activity in decidua basalis did not change during gestation, while activity in endometrium was found to increase by a factor of 5.3 (P less than 0.001), from early to late gestation. The increases, both in estrogen sulfatase activity in chorion, endometrium and placenta and in steroid sulfatase activity in endometrium, occurred primarily within the final 3 weeks of gestation. In contrast, the decrease in estrogen sulfatase activity in amnion occurred principally between the fifth and sixth weeks of gestation. Analysis of radiolabelled metabolites indicated that estradiol and progesterone could be produced via estrogen sulfatase and steroid sulfatase activities in certain tissues. Subcellular fractionation of tissues revealed that the greatest specific activity and total activity, in all cases, was associated with the 105,000 g pellet. Significant activity was also detected in the 750 and 10,000 g pellets but not in the 105,000 g supernatant. Radioimmunoassay of endogenous estradiol-17 beta (estradiol) in chorion extracts revealed a 6.3-fold increase in the hormone from mid to late gestation. Estradiol levels in endometrium and myometrium did not appear to change during this time. It was concluded that increased estrogen sulfatase activity in guinea pig chorion in late gestation occurs along with elevated levels of the hormone estradiol which may be important for parturition in this species.     

Sulfation by guinea pig chorion and uterus: Differential action towards estrone and estradiol

The activities of estrogen sulfotransferase, estrogen sulfatase and estradiol 17β-dehydrogenase change considerably in the guinea pig uterine compartment during gestation. This study was undertaken to enquire if the chorion membrane could influence the pattern of estrogen resulting when substrates were applied to the fetal surface of the chorion while it was attached, late in gestation, to the uterine wall. This tissue system resulted in a differential handling of estrone and estradiol. Estrone was largely excluded from the tissue, remaining mainly in free steroidal form. Estradiol was considerably converted to its 3-sulfate which was mainly retained by the chorion. Parallel experiments with chorion and uterus separately failed to discriminate between the two substrates. Hydrolysis of estrone sulfate and estradiol 3-sulfate was similar in all three tissue systems. It appears that the interaction of chorion with uterus late in gestation causes a difference in tissue action towards the two steroid substrates of closely related structure. The results suggest a limitation in tissue uptake of estrone compared with estradiol, or a much greater sulfotransferase activity towards estradiol. Whole cytosols of late gestational chorion catalyzed sulfation of estradiol at about double the velocity of estrone. This may only partly account for the difference in the intact chorion-uterine tissue system.     

Heterogeneity of guinea pig chorion and liver estrogen sulfotransferases

The presence of two forms of estrogen sulfotransferase (EST) in 105,000 g cytosols of guinea pig chorion and liver has been established by chromatofocusing via a fast protein liquid chromatographic (FPLC) procedure. The chorion EST forms were eluted at pH 6.2 and 5.4, and the liver forms at 6.1 and 5.3. Each has been further purified by an affinity column step using Agarose-hexane-adenosine-3',5'-diphosphate (PAP-Agarose) gel to achieve up to 386-fold and 77-fold specific activity (SA) increases over cytosol for chorion and liver, respectively. The most highly purified preparations were extremely unstable unless protected by the addition of serum albumin of high purity. Each EST form exhibited an estimated molecular weight of 48-52 KDa by FPLC gel filtration and each acted upon both estrone (E1) and estradiol (E2). Each of these steroids inhibited sulfation of the other. A departure from Michaelis-Menten kinetics occurred, particularly in the case of chorion EST, at steroid substrate concentrations above 0.1-0.15 microM. E2 caused strong substrate inhibition of the most highly purified chorion EST. Chorion EST possessed considerable affinity for E1 and E2.     

Changing 17 beta-hydroxysteroid dehydrogenase activity in preimplantation rat and mouse embryos

The 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity in rat and mouse preimplantation embryos was determined by measuring the interconversion of estradiol (E2) and estrone (E1). Rat and mouse embryos were cultured in medium containing 450 nM [3H]E1 or -E2 and the amount of [3H]E1 and -E2 in the medium at the end of the first hour was determined. The results showed that in both species 17 beta-HSD activity was detectable from the one-cell stage (Day 1) onward. In the rat, 17 beta-HSD effected primarily E2----E1 conversion, with the activity decreasing from Day 1 to Day 5. In the mouse, we found primarily E1----E2 conversion from Day 1 to the morning of Day 4, then E2----E1 increased sharply to near the E1----E2 rate in the evening of Day 4 and surpassed the E1----E2 rate the next morning. It seems that: 1) 17 beta-HSD is active throughout the entire preimplantation period, and 2) the enzyme activity changes during preimplantation development. Thus, the rat and mouse preimplantation embryo could regulate the E1- to -E2 ratio in the embryos and in their environment.     

Timing of ovulations in the superovulated bovine

Plasma levels of estrone sulfate, estrone and estradiol, and progesterone were measured in six ewes throughout pregnancy. Estrone sulfate was detectable at around 70 days of gestation with values ranging between 0.3 – 0.7 pmol (0.1 – 0.3 ng) per ml. The level increased steadily to between 3 – 24 pmol (1 – 9 ng) per ml at about 2 days before lambing. An upsurge then followed reaching a maximal concentration between 40 – 130 pmol (15 – 50 ng) per ml. Unconjugated estrone and estradiol levels were appreciable only in the last 2–3 days of pregnancy and the profiles at this time followed closely that of estrone sulfate so that the molar ratio of estrone sulfate: estrone: estradiol remained remarkably constant at approximately 100:2:1 in spite of the great individual variations in absolute concentrations.The progesterone level was higher than that of estrone sulfate throughout pregnancy except 1–2 days prior to parturition. The sharp decline in progesterone concentration in the last two days coincided with the upsurge of estrone sulfate, but the net decrease in concentration was only about one-third of the net increase in estrone sulfate concentration during this period. These data are discussed in relation to the possible role of estrone sulfate and the possibility of placental conversion of progesterone to estrone sulfate during late pregnancy in the ewe.     

Estradiol formation by human osteoblasts via multiple pathways: relation with osteoblast function.

The importance of estrogens in bone metabolism is illustrated by the accelerated bone loss and increase in osteoporotic fractures associated with postmenopausal estrogen deficiency. In this study, the expression and activity of the enzymes involved in estrogen metabolism in human osteoblastic cells were investigated in relation to differentiation of these cells. PCR reactions using mRNA from an in vitro differentiating human cell line (SV-HFO) were performed to assess mRNA expression of the enzymes aromatase, different subtypes of 17beta-hydroxysteroid dehydrogenase (17beta-HSD), and steroid sulfatase. Aromatase, sulfatase, and 17beta-HSD type 2 and 4 were found to be expressed throughout differentiation. Expression of 17beta-HSD type 3, however, was relatively weak, except for early time points in differentiation. Type 1 17beta-HSD expression was not detected. Aromatase activity decreased during differentiation, as was demonstrated by the conversion of androstenedione (A) and testosterone (T) into estrone (E(1)) and estradiol (E(2)), respectively. The 17beta-HSD isozymes catalysing a reductive reaction convert androstenedione and estrone into testosterone and estradiol, respectively. Their activity declined with differentiation. Analysis of 17beta-HSD activity indicated both oxidative (E(2) to E(1); T to A) and reductive (E(1) to E(2); A to T) metabolism at all stages of osteoblast differentiation. Both activities declined as cells moved toward a differentiating mineralizing phenotype. However, the oxidative reaction was increasingly in favor of the reductive reaction at all times during differentiation. Sulfatase activity, as demonstrated by the conversion of estrone-sulfate into estrone, was constant during differentiation. In conclusion, we have demonstrated that all enzymes necessary for estrogen metabolism are expressed and biologically active in differentiating human osteoblasts. The activity of aromatase and 17beta-HSD was found to be dependent on the stage of cell differentiation. In addition, human osteoblasts effectively convert estradiol into estrone. The efficacy of osteoblasts to synthesize estradiol may determine the ultimate change in rate of bone turnover after menopause, as well as the development of osteoporosis. Moreover, the enzymes involved in the metabolism of estradiol may form a target for intervention.     

Tissue-specific concentration changes of estrone and estradiol during spontaneous and ACTH-induced parturition in sheep

Changes in estrogen production are considered important in the sequence of events leading to parturition. We sought tissue-specific changes in the concentration of unconjugated estrone (E1) and estradiol (E2) in intrauterine fetal (amnion, chorion) and maternal (endometrium, myometrium) tissues during normal pregnancy, labour, and ACTH-induced labour in sheep. The mean concentrations of E1 and E2 in the fetal membranes were higher than in endometrium and myometrium. In amnion there were no consistent changes in estrone concentrations with gestation, although estradiol concentrations increased between day 130 and term. In the endometrium there were increases in both estrone and estradiol between day 100 and term, whereas in the myometrium increases in the concentrations of E1 and E2 occurred between days 130-135 and term. Animals showing a labourlike pattern of uterine contractions after intrafetal ACTH administration did not show significant differences in estrone or estradiol concentrations in amnion, chorion, or endometrium compared with saline-infused controls. However, there was a progressive increase in the concentration of estrone and estradiol in the myometrium during ACTH-induced labour. We conclude that changes in the concentrations of estrone and estradiol in intrauterine tissues vary between the tissues studied and the two estrogens. In general, estrogen concentrations increased towards term, but this trend was more marked in the maternal than fetal tissues. The changes in estrone concentrations in myometrium, but not in the other tissues, were replicated during ACTH-induced labour. Our results would be compatible with the suggestion that tissue-specific changes in estrogen concentrations may contribute to the local intrauterine steroid milieu during pregnancy and at term.     

Evidence for sulfatase and 17beta-hydroxysteroid dehydrogenase type 1 activities in equine epididymis and uterus

Our previous work showed that stallion testis produces high amounts of estrogens which are subsequently found in the ejaculate. These estrogens are mainly synthesized by testicular aromatase, and the major estrogen produced is estrone sulfate (E1S). The objective of this study was to investigate the potential role of E1S as a source of estrogens in the male and female horse reproductive tracts by determining whether both estrone sulfatase (Sulf) and 17beta-hydroxysteroid dehydrogenase type I (17beta-HSD1) activities were present in equine testes, epididymis and uterus. We assessed E1S bioconversion into estrone (E1) and estradiol (E2) in these tissues. Both Sulf and 17beta-HSD1 activities were well detected in the cauda epididymis and uterus. Additionally, Sulf activity was present in the distal corpus of the epididymis, and 17beta-HSDI in the proximal corpus. In contrast, aromatase gene expression, measured as an internal control of endogenous estrogen production, had high activity only in the testis. We found that seminal E1S of testicular origin can be metabolized to E2, especially in the cauda epididymis and uterus. Because E2 appears to play a major role in male and female reproduction, we propose that the bioconversion of seminal E1S could affect male and female fertility.     

Possible function of 17 beta-hydroxysteroid dehydrogenase in preimplantation hamster embryos

17 beta-Hydroxysteroid dehydrogenase (17 beta-HSD) catalyzes the interconversion of estradiol-17 beta (E2) and estrone (E1). The present study is designed to investigate the following: (1) the developmental stage of hamster embryos at which 17 beta-HSD activity first becomes detectable, and (2) the E1----E2 and E2----E1 conversion rate in the preimplantation hamster embryo. Embryos obtained from superovulated hamsters on days 1-4 were cultured in medium containing 107 ng [3H]E1 or -E2/ml and the respective conversion product, [3H]E2 or -E1, was isolated and assayed. The results show that (1) E1----E2 conversion was active in all embryos at the rate of 0.57, 0.66, 0.54 and 0.48 fmol/embryo/hr for day 1 (one-cell), 2 (two-cell), 3 (eight-cell) and 4 (blastocyst), respectively, and (2) E2----E1 conversion was not detectable in hamster embryos. In long-term blastocyst culture, E2----E1 conversion becomes detectable at 25 hours and increases sharply from 25 to 47 hours. These results suggest that (1) 17 beta-HSD may function mainly to convert E1 into E2 in preimplantation hamster embryos and (2) E2----E1 conversion may become active only during and after implantation.     

Peripheral changes in estrone sulfate concentration during the first trimester of gestation in cattle: comparison with unconjugated estrogens and relationship to fetal number

Estrone sulfate originates mainly in the conceptus during gestation in cattle. Its concentration in maternal body fluids is a useful indicator of placental function. The objective of this study was to determine the profiles of estrone sulfate during early gestation in singleton and twin bearing cows using a newly developed extraction method. One or two blastocysts produced in vitro were nonsurgically transferred to regularly cycling Holstein cows on Day 7 (Day 0 was defined as the first day of standing estrus). Pregnancy was diagnosed on Days 30, 45 and 60 by transrectal ultrasonography and finally confirmed at parturition. Six cows with singleton and six with twin pregnancies were used in the experiment. Blood was collected every other morning by jugular venipuncture from the day after transfer to Day 100. Harvested plasma was applied to reversed-phase C18 cartridges. Estrone sulfate and unconjugated estrogens (estrone and estradiol-17beta) retained in the cartridge were eluted separately by methanol stepwise gradient and each measured by validated radioimmunoassay. On average, estrone sulfate concentrations fluctuated between 2 and 6 pg/ml until Day 50 in both groups and then gradually increased. However, the levels of estrone and estradiol- 17beta remained low (1-5 pg/ml) until Day 80. The concentration of estrone sulfate after Day 50 was significantly affected by the day of gestation (P < 0.0001) and the number of fetuses (P < 0.01). After Day 80. estrone sulfate increased drastically, followed by increases in estrone and estradiol-17beta concentrations. The rate of increase in estrone sulfate during Days 80-100 was the greatest among all estrogens (P < 0.05). The rates of increase in estrone sulfate during Days 50-80 and 80-100 were 1.7 times greater in twin pregnancies than in cows having one fetus. These results suggest that the concentration of estrone sulfate in bovine peripheral blood plasma during early gestation has potential application in monitoring embryonic growth as well as fetoplacental development.     

Estrogen sulfotransferase activity in guinea pig uterus and chorion

An estrogen sulfotransferase (ST) is detectable in high speed supernatants of pregnant guinea-pig uterus and shows maximum activity between about 47 and 55 days of gestation, with a decrease toward term. No appreciable activity was apparent in the non-pregnant state or before at least 43 days of pregnancy. A considerably higher ST activity is present in chorion as early as 30 days of gestation, and this also decreases toward term. The two ST's exhibit similar KM (0.1-0.13 microM with estrone as substrate) and pI (5.8) values, as well as similar specificities. Estradiol-17 beta and estriol are sulfurylated 82 and 6% that of estrone at equimolar concn. Neither p-nitrophenol nor several neutral steroids are substrates for the enzymes. Enzyme activity is poorly expressed in the absence of thiol groups, the presence of monothioglycerol stimulating uterine and chorion enzymes by 5- and 15-fold, respectively. Stimulation is also observed in the presence of Mg2+, Ca2+ or Mn2+. Chromatofocusing on a poly buffer ion-exchanger from pH 7.4 to 4.0 resulted in elution of a sharp peak of enzyme activity, at pH = 5.8, from both tissues provided that the eluting buffer contained thiol groups and 0.25 M sucrose. This single step resulted in at least a 35- to 100-fold increase in specific activity. The partially purified enzyme from chorion exhibited a KM for estrone of 0.13 microM.     

Estradiol and estrone C-16 derivatives as inhibitors of type 1 17beta-hydroxysteroid dehydrogenase: blocking of ER+ breast cancer cell proliferation induced by estrone

Estrogens play an important role in the development of breast cancer. Inhibiting 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1)--the enzyme responsible for the last step in the biosynthesis of the most potent estrogen, estradiol (E2)--would thus allow hindering the growth of estrogen-sensitive tumors. Based on a previous study identifying 16beta-benzyl-E2 (1) as a lead compound for developing inhibitors of the transformation of estrone (E1) into E2, we modified the benzyl group of 1 to improve its inhibitory activity. Three strategies were also devised to produce compounds with less residual estrogenic activity: (1) replacing the hydroxy group by a hydrogen at position 3 (C3); (2) adding a methoxy at C2; and (3) adding an alkylamide chain known to be antiestrogenic at C7. In order to test the inhibitory potency of the new compounds, we used the human breast cancer cell line T-47D, which exerts a strong endogenous 17beta-HSD1 activity. In this intact cell model, 16beta-m-carbamoylbenzyl-E2 (4m) emerged as a potent inhibitor of 17beta-HSD1 with an IC50 value of 44 nM for the transformation of [14C]-E1 (60 nM) into [14C]-E2 (24-h incubation). In another assay aimed at assessing the unwanted estrogenic activity, a 10-day treatment with 4m at a concentration of 0.5 microM induced some proliferation (38%) of T-47D estrogen-sensitive (ER+) breast cancer cells. Interestingly, when 4m (0.5 microM) was given with E1 (0.1 nM) in a 10-day treatment, it blocked 62% of the T-47D cell proliferation induced by E1 after its reduction to E2 by 17beta-HSD1. Thus, in addition to generating useful structure-activity relationships for the development of 17beta-HSD1 inhibitors, our study demonstrates that using such inhibitors is a valuable strategy for reducing the level of E2 and consequently its proliferative effect in T-47D ER+ breast cancer cells.     

Endocrine profiles during the estrous cycle and pregnancy in the Baird's tapir (Tapirus bairdii)

Serum samples were collected 1–3 times weekly from two Baird's tapirs (Tapirus bairdii) for 6 months in 1987–1988, and for more than 3 consecutive years beginning in 1989 to characterize hormone patterns during the estrous cycle and pregnancy. Based on serum progesterone concentrations, mean (±SEM) duration of the estrous cycle (n = 20) was 30.8 ± 2.6 days (range, 25–38 days) with a luteal phase length of 18.1 ± 0.4 days (range, 15–20 days). Mean peak serum progesterone concentrations during the luteal phase were 1.35 ± 0.16 ng/ml, and nadir concentrations were 0.19 ± 0.03 ng/ml during the interluteal period. Distinct surges of estradiol preceded luteal phase progesterone increases in most (14/20) cycles. Gestation length was 392 ± 4 days for three complete pregnancies. Mean serum progesterone concentrations increased throughout gestation and were 1.83 ± 0.13, 2.73 ± 0.13, and 4.30 ± 0.16 ng/ml during early, mid- and late gestation, respectively. Serum estradiol concentrations began to rise during mid-gestation, increasing dramatically during the last week of pregnancy. Patterns of serum estriol and estrone secretion during pregnancy were similar to that observed for estradiol. In contrast to progesterone and estrogens, serum cortisol concentrations were unchanged during pregnancy or parturition. Females resumed cycling 16.2 ± 2.0 days after parturition (n = 4) and, on two occasions, females became pregnant during the first postpartum estrus. These data suggest that the tapir cycles at approximately monthly intervals and that increases in serum progesterone are indicative of luteal activity. The interluteal period is relatively long, comprising approximately 40% of the estrous cycle. During gestation, progesterone concentrations are increased above luteal phase levels, and there is evidence of increased estrogen production during late gestation. The absence of increased cortisol secretion at the end of gestation suggests that this steroid does not play a major role in initiating parturition in this species. © 1994 Wiley-Liss, Inc.     

Endocrine changes during pregnancy, parturition and post-partum in guanacos (Lama guanicoe)

Plasma concentrations of progesterone (P4), estradiol-17β (E2), estrone (E1) and estrone sulfate (E1S) were measured during gestation in eight guanacos kept in captivity. Gestational length was 346.1 ± 9.8 days. P4 plasma concentrations increased after ovulation and remained elevated until parturition. However, during the last 4 weeks of gestation, a gradual decrease from 4.17 × 1.17^±1 nmol/L to 2.02 × 1.95^±1 nmol/L on day 5 before parturition was observed, followed by a more abrupt final decline to baseline concentrations which were reached on the day after parturition. Mean E2 plasma concentrations started to increase during the eighth month of gestation, and were significantly elevated up to maximum concentrations of 484.7 × 1.21^±1 pmol/L during the last 2 months of pregnancy. Concentrations returned to baseline during the last 2 days of gestation. An increase of E1S concentrations (p < 0.01) was observed in the eleventh month of gestation. Mean E1S concentrations remained rather constant during the last 3 weeks of gestation between 4 to 8 nmol/L until parturition, when a steep precipitous decline was observed. E1 concentrations were slightly elevated during the last 4 weeks of gestation, however, maximum concentrations did not exceed 1.5 nmol/L. The results show distinct species specific features of gestational steroid hormone profiles in the guanaco in comparison to domestic South American camelids, such as a more pronounced gradual prepartal decrease of P4 concentrations prior to the final decline to baseline, and clearly lesser E1S concentrations during the last 4 weeks of gestation, which lack a continuous prepartal increase.     

Synthesis, biochemical evaluation and rationalisation of the inhibitory activity of a range of 4-hydroxyphenyl ketones as potent and specific inhibitors of the type 3 of 17beta-hydroxysteroid dehydrogenase (17beta-HSD3)

We report the synthesis and biochemical evaluation of a number of 4-hydroxyphenyl ketones as potential inhibitors of the enzyme 17beta-hydroxysteroid dehydrogenase (17beta-HSD). In particular, we evaluated compounds against the catalysis of the conversion of androstenedione (AD) to testosterone (T) [17beta-HSD type 3 (17beta-HSD3)], furthermore, in an effort to determine the specificity of our compounds, we evaluated the ability of the compounds to inhibit the catalysis of the conversion of estrone (E1) to estradiol (E2) [17beta-HSD type 1 (17beta-HSD1)] as well as the conversion of dehydroepiandrosterone (DHEA) to AD [by 3beta-hydroxysteroid dehydrogenase (3beta-HSD)]. The results of our study suggest that the synthesised compounds are, in general, able to inhibit 17beta-HSD3 whilst being weak inhibitors of 17beta-HSD1. Against 3beta-HSD, we discovered that all of the synthesised compounds were weak inhibitors (all were found to possess less than 50% inhibition at [I]=500 microM). More specifically, we discovered that 1-(4-hydroxy-phenyl)-nonan-1-one (15) was the most potent against 17beta-HSD3 (IC(50)=2.9 microM) whilst possessing poor inhibitory activity against 17beta-HSD1 ( approximately 36% inhibitory activity against this reaction at [I]=100 microM) and less than 10% inhibition for the conversion of DHEA to AD. We have therefore provided good lead compounds in the design and synthesis of novel non-steroidal inhibitors of 17beta-HSD3.     

Development of fetal rat ovaries responsiveness to LH during organ culture.

The responsiveness of fetal neonatal rat ovaries to LH was investigated in vitro using three complementary approaches. First, steroid production was assessed after culture. In control media, detectable levels of estrogens (estradiol and estrone) and progesterone were only observed from day 6 postpartum and during the second week of life respectively. In the presence of LH (100 ng/ml) ovaries produced both estrogens and progesterone from day 4 postpartum and the response to LH was enhanced with IBMX supplementation in the medium. Second, 3 beta-HSD activity was measured with either LH or (Bu)2 cAMP (1mM). Irrespective to the time-period studies (Bu)2 cAMP stimulated this enzyme whereas the stimulation with LH occurred only from day 5 postpartum Third, specific hCG binding was assessed and we found that it occurred only on days 7 and 10. However, when fetal ovaries were pretreated for 48 h with (Bu)2 cAMP, a specific hCG binding could be detected and progesterone production was enhanced in response to LH. An effect of the nucleotide via a stimulation of the neuraminidase activity did not seem to be involved. Lastly treatment of 18-day-old fetal ovaries with cholera toxin (10nM) or forskolin (1 microM) was found to stimulate progesterone production and VIP (0.1 to 1 microM) stimulated both the 3-HSD activity and the estradiol production. These data suggest that the absence of steroidogenic response to LH before day 4 postpartum could be explained by the absence of receptors, though the LH transmembrane signal-transduction system is functional in fetal ovaries.(ABSTRACT TRUNCATED AT 250 WORDS)     

Novel inhibitors of 17beta-hydroxysteroid dehydrogenase type 1: templates for design

The 17beta-hydroxysteroid dehydrogenases (17beta-HSDs) catalyze the interconversion between the oxidized and reduced forms of androgens and estrogens at the 17 position. The 17beta-HSD type 1 enzyme (17beta-HSD1) catalyzes the reduction of estrone (E1) to estradiol and is expressed in malignant breast cells. Inhibitors of this enzyme thus have potential as treatments for hormone dependent breast cancer. Syntheses and biological evaluation of novel non-steroidal inhibitors designed to mimic the E1 template are reported using information from potent steroidal inhibitors. Of the templates investigated biphenyl ethanone was promising and led to inhibitors with IC(50) values in the low micromolar range.     

Role of 17 beta-hydroxysteroid dehydrogenase in the modulation of nuclear estradiol receptor binding by progesterone in the rat anterior pituitary gland and the uterus

Progesterone has been shown to decrease occupied pituitary and uterine nuclear estradiol receptor (E2R) binding in mature and immature estrogen-primed rats. Progesterone has also been shown to stimulate pituitary but not uterine 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) in the rat. The conversion of estradiol to its less active metabolite estrone by 17 beta-HSD and activation of phosphatase are among mechanisms considered to be involved in the reduction of E2R. To determine if 17 beta-HSD stimulation was a mechanism by which progesterone induced nuclear E2R decrease, the synthetic estrogen ethinylestradiol, which is not oxidized by 17 beta-HSD, was used instead of estradiol to prime adult ovariectomized rats. When ethinylestradiol-primed rats received 0.8, 2.0 or 4.0 mg/kg body wt of progesterone 2 h before sacrifice, the total and occupied nuclear E2R accumulation in the anterior pituitary by a subsequent ethinylestradiol injection 1 h later did not show any decrease. This response was different from that observed previously in estradiol-primed animals in which progesterone showed a multiphasic decrease of occupied form of nuclear E2R. However, in the uterus of ethinylestradiol-primed rats, a partial decrease of total and occupied nuclear E2R accumulation was observed in the presence of the three doses of progesterone used. The decrease of uterine nuclear E2R with the three progesterone doses was different from the dose-dependent effect of progesterone observed in the uterus of estradiol-primed rats. Affinity constants of the interaction between [3H]estradiol and the nuclear E2R were similar among groups treated with ethinylestradiol, estradiol and progesterone. These results demonstrate the involvement of 17 beta-HSD in the reduction of anterior pituitary gland E2R by progesterone in the estradiol-treated animals. Furthermore, the mechanism of decrease of E2R by progesterone in the uterus appears to be different from the pituitary gland.     

Urinary steroids in the periparturient and postpartum periods through early pregnancy in llamas

Urinary steroids were determined daily in the periparturient and postpartum periods, including early pregnancy, in the female llama. Estrone sulfate (E(1)S) and pregnanediol glucuronide (PdG) concentrations were determined by enzyme immunoassay with values corrected for variations in urine concentration by creatinine. Estrone sulfate concentrations, elevated during the last 20 days of gestation through 12 hours before parturition, were declining at the time of delivery. Pregnanediol glucuronide concentrations followed a pattern similar to that of estrone sulfate except that values began to decrease 5 days before parturition. Values for both E(1)S and PdG were basal by 24 hours after delivery. The first significant elevation of estrone sulfate, indicative of initial follicle development, was observed 5 days after parturition. Pregnanediol glucuronide concentrations were low during the postpartum period until 4 to 5 days after breeding. The PdG values rose steadily following copulatory-induced ovulation, which was initiated at about 2 weeks postpartum; values continued to increase through the first 15 days of pregnancy.     

Localization of type 7 17beta-hydroxysteroid dehydrogenase in mouse tissues. In situ hybridization studies

The enzyme type 7 17beta-hydroxysteroid dehydrogenase (17beta-HSD) selectively catalyzes the conversion of estrone (E1) into estradiol (E2). In order to obtain detailed information about the exact sites of action of type 7 17beta-HSD, we have studied the cellular localization of type 7 17beta-HSD mRNA in mouse tissues using in situ hybridization (ISH). In parallel studies, we also measured the enzyme mRNA levels by quantitative real time (RT)-PCR. In the ovary, strong hybridization signal was restricted to corpus luteum cells. In the female mammary gland, type 7 17beta-HSD mRNA was found to be expressed in stromal cells surrounding the ducts. In the clitoral and preputial glands, specific labeling was observed in the epithelial cells of both acini and small ducts. In the adrenal gland, hybridization signal was observed in the zona fasciculata and reticularis in the cortex. In the liver, hybridization signal was found in all the hepatocytes. In the colon, type 7 17beta-HSD mRNA expression was restricted to epithelial cells of the mucosa. From the results obtained with quantitative real time RT-PCR, it appears, with a very few exceptions, that in tissues exhibiting low mRNA expression no ISH signal could be detected. The present data suggest that E2 can be formed through the action of type 7 17beta-HSD in specific cell types in the ovary and peripheral tissues, in addition to type 1 17beta-HSD, thus providing tissues with an alternative route of formation of E2.