Effects of single pesticides and binary pesticide mixtures on estrone production in H295R cells.

The aim of the present study was to determine whether the human adrenocortical carcinoma cell line H295R can be used as an in vitro test system to investigate the effects of binary pesticide combinations on estrone production as biological endpoint. In the first step ten pesticides selected according to a tiered approach were tested individually. The anilinopyrimidines cyprodinil and pyrimethanil as well as the dicarboximides iprodione and procymidone increased estrone concentration, while the triazoles myclobutanil and tebuconazole as well as the strobilurins azoxystrobin and kresoxim-methyl decreased estrone concentration in the supernatant of H295R cells. The N-methylcarbamate methomyl did not show any effects, and the phthalimide captan reduced estrone concentration unspecifically due to its detrimental impact on cellular viability. When cyprodinil and pyrimethanil, which belong to the same chemical group and increase estrone production, were combined, in most of the cases the overall effect was solely determined by the most potent compound in the mixture (i.e., cyprodinil). When cyprodinil and procymidone, which belong to different chemical groups but increase estrone production, were combined, in most cases an additive effect was observed. When cyprodinil, which increased estrone production, was combined with either myclobutanil or azoxystrobin, which decreased estrone production, the overall effect of the mixture was in most cases either entirely determined by myclobutanil or at least partially modulated by azoxystrobin. In conclusion, H295R cells appear to be an adequate in vitro test system to study the effect of combining two pesticides affecting estrone production.

Sex steroid hormones in pairs of tumor and serum from breast cancer patients and pathobiological role of androstene-3ß, 17ß-diol.

Estrogens play an important role in the pathobiology of breast cancer. In postmenopausal women, peripheral synthesis of estrogens from adrenal/ovarian androgens, dehydroepiandrosterone (DHEA) or androstenedione (Adione), by estrogen-metabolizing enzymes is important. Besides estrone (E1) and estradiol (E2), androgen metabolites, such as androstene-3ß, 17ß-diol (Aenediol) or 5α-androstane-3ß, 17ß-diol (Aanediol), are known to have estrogenic functions, although they have been studied much less in breast cancer. To precisely elucidate steroid metabolism in breast cancer patients and to identify the pathobiological role of estrogenic androgen metabolites, concentrations of DHEA, Adione, Aenediol, Aanediol, E1, and E2 in pairs of serum and tumor tissue from patients with primary breast cancer were measured by liquid chromatography-tandem mass spectrometry. Cell proliferation assays using Aenediol were performed for four breast cancer cell lines. Serous E2 concentration was extremely low in postmenopausal women; however, a marked increase in tumor tissue was observed in hormone receptor-positive cases. E1 concentration, in contrast, was sustained at a higher level, even in postmenopausal serum, and did not increase in tumor tissue irrespective of the hormone receptor status. Dehydroepiandrosterone was most abundant in all samples, and exhibited a similar pattern as Adione and Aenediol. 5α-Androstane-3ß, 17ß-diol was undetectable in most samples. Androstene-3ß, 17ß-diol proliferated estrogen receptor-apositive breast cancer cells in the absence of E2. The intratumoral increase of E2, but not E1, in hormone receptor-positive postmenopausal breast cancer tissue, as well as the proliferative role of Aenediol, was elucidated.

A common polymorphism in the human aromatase gene alters the risk for polycystic ovary syndrome and modifies aromatase activity in vitro.

Aromatase is a key enzyme involved in estradiol and estrone biosynthesis. Given that polymorphisms of the CYP19A1 gene encoding aromatase have been correlated with plasma testosterone levels, CYP19A1 may therefore act as a genetic modifier of the hyperandrogenic phenotype of polycystic ovary syndrome (PCOS). However, no functional CYP19A1 polymorphisms that predict the risk of PCOS have been identified. We explored the role of CYP19A1 genetic variation in a large case-control study involving 1078 samples, in which five common genetic polymorphisms were scored. Human embryonic kidney 293 cells were transiently transfected with a vector encoding either the CYP19A1 wild-type (WT) allele or an Arg(264)Cys variant to evaluate aromatase activity. Cells were cultured with androstenedione and estrone levels were measured using a specific ELISA. The Arg(264)Cys variant of CYP19A1 (rs700519) is associated with PCOS (P= 0.004, corrected P = 0.02). In this functional study, when cells were cultured in varying concentrations of androstenedione (100, 400 and 500 nM), transfection with the Arg(264)Cys variant resulted in increased conversion of androstenedione to estrogen when compared with transfection with the WT construct (P< 0.001). Our data suggest that the common missense polymorphism rs710059 is associated with susceptibility to PCOS and that the Arg(264)Cys variant may increase aromatase enzymatic activity. Overall, these findings imply that aromatase plays an important role in PCOS.

Rosiglitazone and pioglitazone inhibit estrogen synthesis in human granulosa cells by interfering with androgen binding to aromatase.

The effects of rosiglitazone or pioglitazone (thiazolidinediones, TZDs) on estrogen production and aromatase activity in human ovarian cells were examined. Human granulosa cells were incubated in the tissue culture medium supplemented with androstenedione or testosterone, with or without insulin, TZDs, or type 1 17ß-hydroxysteroid-dehydrogenase (17ß-HSD) inhibitor. Estrogen concentrations in the conditioned medium, aromatase mRNA and protein expression in the cells and androgen substrate binding to aromatase were measured. With androstenedione as substrate, rosiglitazone or pioglitazone inhibited estrone production by up to 22% (p<0.012) while type 1 17ß-HSD inhibitor enhanced this effect of rosiglitazone or pioglitazone by 37% (p<0.001) and by 67% (p<0.001), respectively. With testosterone as substrate, rosiglitazone or pioglitazone inhibited estradiol production by 32% (p<0.001). With (3)H-testosterone as substrate, rosiglitazone or pioglitazone inhibited the (3)H-tritiated water release by the cultured cells by 45% and 35%, respectively, thus directly demonstrating inhibition of aromatase. Rosiglitazone or pioglitazone, however, had no significant effect on aromatase mRNA or protein expression. Rosiglitazone or pioglitazone inhibited (125)I-androstenedione and (125)I-testosterone binding to aromatase by 38% (p<0.001). It was concluded that rosiglitazone or pioglitazone inhibit estrogen synthesis in human granulosa cells by interfering with androgen binding to aromatase.

Estrogen suppression in premenopausal women following 8 weeks of treatment with exemestane and triptorelin versus triptorelin alone.

INTRODUCTION: Luteinizing hormone-releasing hormone (LHRH) agonists (e.g., triptorelin) reduce ovarian estrogen production in premenopausal women with hormone-sensitive breast cancer. Aromatase inhibitors (e.g., exemestane) inhibit extraovarian production of estrogen and may further reduce circulating estrogens when combined with an LHRH agonist. METHODS: Healthy premenopausal women were randomized to receive 3.75 mg triptorelin (T) on days 1 and 29 with 25 mg exemestane (EX) or matched placebo once daily for 8 weeks, from day 1 to day 56. The primary objective was to evaluate the effect of T +/- EX on estradiol (E(2)) suppression by comparing the AUC(day 36-57 )for the 2 treatments. Secondary objectives included evaluation of estrone (E(1)), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) suppression; effects of EX on the T-induced gonadotrophin and estrogen flare; pharmacokinetics (PK); and safety. RESULTS: Twenty-eight (14 in each arm) were evaluable for efficacy and PK. Mean plasma estrogen levels (AUC(day 36-57)) were significantly lower for subjects who received T + EX than for subjects who received T alone (20.6 vs. 54.0 pg d/ml [-62%; P < 0.05], and 38.9 vs. 198.0 pg d/ml [-80%; P < 0.01] for E(2) and E(1), respectively). Coadministration of EX did not affect the initial flare or subsequent suppression of LH and FSH following the first dose of T, or the PK of T. Both treatments were well tolerated. CONCLUSIONS: Coadministration of T and EX resulted in greater estrogen suppression than when T was given alone. These findings could translate into improved clinical outcomes for premenopausal breast cancer patients receiving LHRH agonists.

Estrogen formation by the isolated perfused rhesus monkey brain.

Perfusion of two isolated brains from immature male rhesus monkeys with [(3)H]androstenedione resulted in the identification of free and conjugated [(3)H]estrone and free [(3)H]estradiol from the perfusates. In the dissected cerebral tissues, estrogens were recovered only from the hypothalamus and limbic system. The production of estrogens from androstenedione during the 40-minute perfusions in these two experiments totaled 1.58 and 2.83 nanograms.

Tissue steroid levels in response to reduced testicular estrogen synthesis in the male pig, Sus scrofa.

Production of steroid hormones is complex and dependent upon steroidogenic enzymes, cofactors, receptors, and transporters expressed within a tissue. Collectively, these factors create an environment for tissue-specific steroid hormone profiles and potentially tissue-specific responses to drug administration. Our objective was to assess steroid production, including sulfated steroid metabolites in the boar testis, prostate, and liver following inhibition of aromatase, the enzyme that converts androgen precursors to estrogens. Boars were treated with the aromatase inhibitor, letrozole from 11 to 16 weeks of age and littermate boars received the canola oil vehicle. Steroid profiles were evaluated in testes, prostate, and livers of 16, 20, and 40 week old boars using liquid chromatography/mass spectrometry. Testis, prostate, and liver had unique steroid profiles in vehicle-treated animals. Only C18 steroid hormones were altered by treatment with the aromatase inhibitor, letrozole; no significant differences were detected in any of the C19 or C21 steroids evaluated. Testis was the only tissue with significantly decreased free estrogens following treatment with the aromatase inhibitor; estrone and estradiol concentrations were lower (p < 0.05) in testes from 16, 20, and 40 week letrozole-treated boars. However, concentrations of the sulfated conjugates, estrone-sulfate and estradiol-sulfate, were significantly decreased (p<0.05) in 16 and 20 week boar testes, prostates, and livers from letrozole-treated boars. Hence, the distribution of estrogens between the free and conjugated forms was altered in a tissue-specific manner following inhibition of aromatase. The results suggest sulfated testicular estrogens are important estrogen precursors for the prostate, potentially enabling peripheral target tissues to synthesize free estrogens in the male pig.

Regulation of P450 oxidoreductase by gonadotropins in rat ovary and its effect on estrogen production.

BACKGROUND: P450 oxidoreductase (POR) catalyzes electron transfer to microsomal P450 enzymes. Its deficiency causes Antley-Bixler syndrome (ABS), and about half the patients with ABS have ambiguous genitalia and/or impaired steroidogenesis. POR mRNA expression is up-regulated when mesenchymal stem cells (MSCs) differentiate into steroidogenic cells, suggesting that the regulation of POR gene expression is important for steroidogenesis. In this context we examined the regulation of POR expression in ovarian granulosa cells by gonadotropins, and its possible role in steroidogenesis. METHODS: Changes in gene expression in MSCs during differentiation into steroidogenic cells were examined by DNA microarray analysis. Changes in mRNA and protein expression of POR in the rat ovary or in granulosa cells induced by gonadotropin treatment were examined by reverse transcription-polymerase chain reaction and western blotting. Effects of transient expression of wild-type or mutant (R457H or V492E) POR proteins on the production of estrone in COS-7 cells were examined in vitro. Effects of POR knockdown were also examined in estrogen producing cell-line, KGN cells. RESULTS: POR mRNA was induced in MSCs following transduction with the SF-1 retrovirus, and was further increased by cAMP treatment. Expression of POR mRNA, as well as Cyp19 mRNA, in the rat ovary were induced by equine chorionic gonadotropin and human chorionic gonadotropin. POR mRNA and protein were also induced by follicle stimulating hormone in primary cultured rat granulosa cells, and the induction pattern was similar to that for aromatase. Transient expression of POR in COS-7 cells, which expressed a constant amount of aromatase protein, greatly increased the rate of conversion of androstenedione to estrone, in a dose-dependent manner. The expression of mutant POR proteins (R457H or V492E), such as those found in ABS patients, had much less effect on aromatase activity than expression of wild-type POR proteins. Knockdown of endogenous POR protein in KGN human granulosa cells led to reduced estrone production, indicating that endogenous POR affected aromatase activity. CONCLUSION: We demonstrated that the expression of POR, together with that of aromatase, was regulated by gonadotropins, and that its induction could up-regulate aromatase activity in the ovary, resulting in a coordinated increase in estrogen production.

Synthesis of steroid hormones in the porcine oviduct during early pregnancy.

Past studies of the oviducts have documented oviductal steroid production during the oestrous cycle in pigs. The present study examined whether the pig oviducts are the source of steroid hormones during early pregnancy. In the ampulla and isthmus, the expression of 3ß-hydroxysteroid dehydrogenase (3ßHSD) and aromatase cytochrome P450 (CYP19) mRNA by real-time PCR, cellular localization and quantities of the studied proteins by immunofluorescence and Western blot analysis, and concentration of steroid hormones in oviductal flushings by radioimmunoassay, were studied. The expression of 3ßHSD in the ampulla and isthmus was correlated (r = 0.89) and higher on Days 2-3 and 15-16 than on Days 10-11 and 12-13. CYP19 expression was elevated in the ampulla on Days 2-3, 10-11 and 15-16 and in the isthmus on Days 2-3 vs. the other days studied. The studied proteins were localized in oviductal epithelial cells. In the ampulla, the quantity of 3ßHSD protein did not change, and was greater in the isthmus on Days 2-3 vs. Days 12-13 of pregnancy. The P450arom protein quantity increased in the ampulla on Days 2-3 vs. Days 10-11 and 15-16 and vs. Days 10-11 and 12-13 in the isthmus. The concentrations of progesterone and androstenedione in oviductal flushings were lowest on Days 12-13 and on Days 2-3 and 15-16, respectively, while oestradiol-17ß and oestrone levels did not change. Porcine oviducts are the sources of steroid hormones during early pregnancy. The expression of steroidogenic enzymes primarily increases during the embryos presence in the oviduct, i.e., on Days 2-3 of pregnancy.

Conversion of blood androgens to estrogens in normal adult men and women.

Continuous infusions of Delta(4)-androstenedione-7-(3)H and testosterone-7-(3)H have been used to demonstrate that these androgens are converted to estrone and 17beta-estradiol, and contribute to the circulating blood levels of these estrogens in normal males and females. The conversion ratio (ratio of concentrations of radioactivity of free product steroid [chi(-PRO)] and free precursor steroid [chi(-PRE)], both corrected for recoveries, after an infusion of radioactive precursor steroid) for androstenedione (precursor) to estrone (product) is 0.013 in males and 0.007 in females, and the conversion ratio for testosterone (precursor) to estradiol (product) is 0.0018 in males and 0.005 in females. The transfer constant, [rho](BB) (AE1), for androstenedione conversion to estrone ([rho](BB) (AE1) = per cent of infused androstenedione, precursor, converted to estrone, product, when infusion and measurement are both in blood) is 1.35% in males and 0.74% in females, and the transfer constant, [rho](BB) (TE2), for testosterone conversion to estradiol is 0.39% in males and 0.15% in females. Whether measured as conversion ratio or transfer constant, the peripheral aromatization of androstenedione takes place to a greater degree than that of testosterone, and, for the respective androgens, both the conversion ratio and [rho](BB) value are greater in males than females. For the androgen interconversions, [rho](BB) (AT) is 4.5% in males and 2.2% in females; [rho](BB) (TA) is 8.2% in males and 12.0% in females. Studies on the distribution coefficients (effective concentration in red cells/plasma) for precursor radioactivity were also made. In both males and females the distribution coefficient for androstenedione is 0.16-0.17 while that of testosterone is 0.01-0.03.

Steroid pathway and oestrone sulphate production in canine inflammatory mammary carcinoma.

Spontaneous canine mammary inflammatory carcinoma (IMC) shares epidemiologic, histopathologic and clinical characteristics with the inflammatory breast carcinoma (IBC) disease in humans. We have analysed the steroids levels in serum and in tissue homogenates of IMC, the expression of two of their receptors (androgen and beta-estrogen) and of three enzymes included in the steroidogenesis pathway (aromatase (CYP19A1), steroid sulphatase (STS) and estrogen sulfotransferase (EST)) trying to explain the specific accumulation of steroids in IMC tissues generating deposits in the form of lipid droplets whose presence can be attributed to steroids secreted by IMC cells. According to our working hypothesis, oestrone sulphate would be the main component of these lipid droplets. The presence of these steroid deposits would contribute to the intense proliferation and invasive behaviour of IMC and IBC, although their involvement in angiogenesis is yet to be demonstrated.

Process for Biotransformation of Androsta-4-ene-3, 17-Dione (4-AD) to Androsta-1,4-Diene-3,17-Dione (ADD).

Androsta-1,4-diene-3,17-dione (androstadienedione, ADD) is key intermediate for the organic synthesis of a variety of female sex hormones such as estrone, estradiol, estriol and other related derivatives. De novo synthesis of this molecule is not yet reported in any form of living system, i.e., microbial, plant, and animal. The structural complexities due to presence of several chiral carbon centers create significant hurdles in chemical synthesis of such molecules. Microbe-mediated biotransformation offer a highly reliable, cost-effective, and relatively non hazardous way for commercial manufacturing of steroidal key intermediates. Currently microbial biotransformations are extensively being exploited for large-scale production of basic intermediates such as androstenedione (AD), ADD, and several types of hydroxylated derivatives of androstane compounds. In this chapter several aspects of microbial biotransformation process of AD to ADD are discussed.

Estrogen inhibits cell proliferation through in situ production in human thymoma.

PURPOSE: We showed previously estrogen receptor (ER) alpha as an independent prognostic marker in human thymoma. Estrogen sulfotransferase (EST), steroid sulfatase (STS), 17beta-hydroxysteroid dehydrogenase (17beta-HSD), and aromatase are considered to play important roles in hormone metabolism of estrogen-dependent tumors. EXPERIMENTAL DESIGN: We examined estrogen production using primary cultures of human thymoma epithelial cells (TEC), intratumoral estradiol (E(2)) concentrations, and status of these enzymes above using immunohistochemistry or semiquantitative reverse transcription-PCR. We then correlated these findings with clinicopathologic variables and/or clinical outcome in 132 patients. RESULTS: E(2) inhibited cell proliferation via ERalpha in TEC, which synthesized estrone and E(2). Intratumoral E(2) concentrations were inversely correlated with EST, positively correlated with STS or 17beta-HSD type 1, and significantly higher in lower-grade or early-stage thymoma. EST status was positively correlated with tumor size, clinical stage, histologic differentiation, and Ki-67 labeling index and significantly associated with adverse clinical outcome and turned out to be a potent independent prognostic factor. STS and/or 17beta-HSD type 1 status was inversely correlated with Ki-67 labeling index and associated with lower histologic grade or early clinical stages. CONCLUSIONS: E(2) inhibits proliferation of TEC through ERalpha, which suggests that E(2) may be effective in treatment of thymoma, especially inoperable tumor, possibly through suppressing its cell proliferation activity. EST status is a potent prognostic factor in thymoma through inactivating estrogens. In situ estrogen synthesis through intracrine mechanism therefore may play important roles in tumorigenesis and/or development of thymoma through regulation of cell proliferation in an intracrine manner.

Endogenous sex hormones and breast cancer in postmenopausal women: reanalysis of nine prospective studies.

BACKGROUND: Reproductive and hormonal factors are involved in the etiology of breast cancer, but there are only a few prospective studies on endogenous sex hormone levels and breast cancer risk. We reanalyzed the worldwide data from prospective studies to examine the relationship between the levels of endogenous sex hormones and breast cancer risk in postmenopausal women. METHODS: We analyzed the individual data from nine prospective studies on 663 women who developed breast cancer and 1765 women who did not. None of the women was taking exogenous sex hormones when their blood was collected to determine hormone levels. The relative risks (RRs) for breast cancer associated with increasing hormone concentrations were estimated by conditional logistic regression on case-control sets matched within each study. Linear trends and heterogeneity of RRs were assessed by two-sided tests or chi-square tests, as appropriate. RESULTS: The risk for breast cancer increased statistically significantly with increasing concentrations of all sex hormones examined: total estradiol, free estradiol, non-sex hormone-binding globulin (SHBG)-bound estradiol (which comprises free and albumin-bound estradiol), estrone, estrone sulfate, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulfate, and testosterone. The RRs for women with increasing quintiles of estradiol concentrations, relative to the lowest quintile, were 1.42 (95% confidence interval [CI] = 1.04 to 1.95), 1.21 (95% CI = 0.89 to 1.66), 1.80 (95% CI = 1.33 to 2.43), and 2.00 (95% CI = 1.47 to 2.71; P(trend)<.001); the RRs for women with increasing quintiles of free estradiol were 1.38 (95% CI = 0.94 to 2.03), 1.84 (95% CI = 1.24 to 2.74), 2.24 (95% CI = 1.53 to 3.27), and 2.58 (95% CI = 1.76 to 3.78; P(trend)<.001). The magnitudes of risk associated with the other estrogens and with the androgens were similar. SHBG was associated with a decrease in breast cancer risk (P(trend) =.041). The increases in risk associated with increased levels of all sex hormones remained after subjects who were diagnosed with breast cancer within 2 years of blood collection were excluded from the analysis. CONCLUSION: Levels of endogenous sex hormones are strongly associated with breast cancer risk in postmenopausal women.

Metabolism of testosterone by GR mouse mammary tumors.

The metabolism of testosterone by GR mouse mammary tumors following serial transplantation was studied. Oophorectomized female recipients were maintained on estrone and progesterone (OEP) or without hormone maintenance (oophorectomized-only group) in order to assess whether the growth of the tumor was hormone dependent (HD) or hormone independent (HI). Tumors in the early generations of the OEP group were HD (generations 1 to 4), which became HI in the latter generations (G5 to G18). All tumors developed in the oophorectomized-only group (generations 1 to 18) were HI. All tumors investigated were capable of metabolizing testosterone to 4-androstenedione, 16 alpha-hydroxytestosterone, 5 alpha-dihydrotestosterone, 5 alpha-androstanedione, and 5 alpha-androstanediol. Total 5 alpha-reduction in OEP group ranged between 50 and 60% of neutral metabolites in HD tumors and dropped to 13 to 28% in HI tumors (generations 5 to 18), similar to the activities (20 to 30%) of the HI tumors in the oophorectomized only group. Different patterns of estrogen synthesis were observed among these tumors. Although tumors showed the presence of appreciable amounts of estriol, estrone was synthesized only in 5 of the 9 HI tumors in the oophorectomized only group. The most striking contrast was that estradiol was synthesized by all HI tumors in the oophorectomized-only group and the OEP group but not in the HD tumors.

Hormones, nutrition, and cancer.

The effects of obesity on steroid metabolism in women with breast and uterine cancer have been considered. Obesity may increase plasma estrone by two mechanisms, a higher rate of secretion of the estrone precursor, androstenedione, and a higher rate of conversion of androstenedione to estrone. Obesity may alter routes of metabolism of androgens and estrogens. The excretion of specific urinary metabolites can therefore be altered by obesity alone. Thus, steroid indices of relative cancer risk or responsiveness must be constructed with due attention to obesity, one of many important variables.

Multiple forms of aromatase and response of breast cancer aromatase to antiplacental aromatase II antibodies.

Two distinct aromatase-active protein complexes are solubilized by use of deoxycholate and separated by diethylamino-ethyl-cellulose chromatography from lyophilized powder of 900 X g precipitate fraction of human term placenta. Aromatase activity to produce estriol, the major estrogen of human pregnancy, was designated to be aromatase I activity and measured by estriol formation from 16 alpha-hydroxytestosterone. Aromatases II activity was the designation for that which produces estrone plus estradiol and was measured by androstenedione aromatization. Aromatases II and I are eluted with 0.25 M and 0.5 M Tris buffer, respectively, from diethylaminoethyl-cellulose column in an Mr 2 million soluble complex. Each has a minimum active Mr 135,000 subunit, which is isolated by Bio-Gel filtration in the presence of detergents, and consists of a reduced nicotinamide adenine dinucleotide phosphate:cytochrome P-450 reductase (Mr 83,000) and a cytochrome P-450 (Mr 52,000). Aromatase II was found to be the major aromatase, containing approximately five times more aromatase activity, reduced nicotinamide adenine dinucleotide phosphate:cytochrome c reductase activity, cytochrome P-450, and protein than did aromatase I. Antibodies raised in rabbits against aromatase II and its reductase suppressed aromatase II activity of breast cancer tissues, as well as of adult male lung tissue, placental microsomes, and solubilized aromatase. The breast carcinoma specimens responded to the antibodies in different degrees, but there was no response to antibodies against rat liver cytochrome P-450. The results indicate similar antigenic structures for breast cancer and placental aromatase but not for rat liver cytochrome P-450.

Estrogen biosynthesis and 1beta-hydroxylation using C19 and 19-nor steroid precursors.

(1) In order to study the relationship between aromatization (estrogen biosynthesis) and 1beta-hydroxylation, the effects of a variety of factors on these processes were evaluated. (2) Using the C18 substrate, 4-estrene-3,17-dione, it was found that carbon monoxide, SU-4885, amphenone B, potassium cyanide, 4-androstene-3,17-dione and 1,4-androstadiene-3,17-dione inhibited the above transformations significantly and to varying degrees. However, within a given experiment the inhibition of each process was similar. (3) SKF-525A did not inhibit either transformation. In addition, phosphate, Tris and barbital buffers, as well as pH changes from 6.9 to 7.7, had no stimulatory or inhibitory effect on the production of estrogen and 1beta-hydroxy compounds. (4) In contrast, several inhibitors affected the aromatization of C19 and C18 steroids differently. These include carbon monoxide, SU-4885 and amphenone B. (5) When a mixture of 4-[7beta-3Hi1estrene-3,17-dione and 19-[4-14C]nortestosterone were incubated together the former was preferentially converted to estrogen. This preference for the 17-keto steroidal form mimics results observed for C19 substrates. (6) We conclude that while estrogen biosynthesis and 1beta-hydroxylation appear to be mediated by the same enzyme system, the same conclusion cannot be drawn for the aromatization of C19 and C18 substrates.

PIP: Estrogen biosynthesis and lbeta-hydroxylation using carbon-19 and 19-nor steroid precursors were evaluated. 4-estrene-3, 17-dione was used to find that carbon monoxide, SU-4885, amphenone B, potassium cyanide, 4-androstene-3,17-dione, and 1,4-androstadiene-3,17-dione inhibited the above transformations to varying degrees. SKF-525A did not inhibit either transformation, and phosphate, Tris and barbital buffers as well as pH changes from 6.9 to 7.7 had no effect on the production of estrogen and lbeta-hydroxy compounds. Carbon monoxide, SU-4885, and amphenone B affected the aromatization of carbon-19 and carbon-18 steroids differently. A mixture of 4 (7 beta-tritium) estrene-3,17-dione and 19-(4-carbon 14) nortestosterone incubated together resulted in the former preferentially converted to estrogen. It is concluded that while estrogen biosynthesis and lbeta-hydroxylation appear to be mediated by the same enzyme system, however, the same conclusion cannot be drawn for the aromatization of carbon-19 and carbon-18 substrates.

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.

Validation of murine and human placental explant cultures for use in sex steroid and phase II conjugation toxicology studies.

Human primary placental explant culture is well established for cytokine signaling and toxicity, but has not been validated for steroidogenic or metabolic toxicology. The technique has never been investigated in the mouse. We characterized human and mouse placental explants for up to 96 h in culture. Explant viability (Lactate dehydrogenase) and sex steroid levels were measured in media using spectrophotometry and ELISA, respectively. Expression and activities of the steroidogenic (3ß-hydroxysteroid dehydrogenase, Cytochrome P45017A1, Cytochrome P45019), conjugation (UDP-glucuronosyltransferase, sulfotransferase (SULT)), and regeneration (ß-glucuronidase, arylsulfatase C (ASC)) enzymes were determined biochemically in tissues with fluorimetric and spectrophotometric assays, and western blot. Explants were viable up to 96 h, but progesterone, estrone, and 17ß-estradiol secretion decreased. Steroidogenic enzyme expression and activities were stable in mouse explants and similar to levels in freshly isolated tissues, but were lower in human explants than in fresh tissue (P<0.01). Human and mouse explants exhibited significantly less conjugation after 96 h, SULT was not detected in the mouse, and neither explants had active ASC, although proteins were expressed. Mouse explants may be useful for steroid biochemistry and endocrine disruption studies, but not metabolic conjugation. In contrast, human explants may be useful for studying conjugation for <48 h, but not for steroid/endocrine studies.