Mechanism of action of contraceptive synthetic progestins

Hyperinsulinemic-euglycemic clamp over the first year of use of depot-medroxyprogesterone acetate as a contraceptive

OBJECTIVE

The literature lacks data on the use of the gold-standard hyperinsulinemic-euglycemic clamp (HEC) technique for the evaluation of insulin resistance (IR) in depot-medroxyprogesterone acetate (DMPA) users. This study assessed carbohydrate metabolism in non-obese users of DMPA using the HEC technique.

STUDY DESIGN

A prospective, non-randomized, comparative study conducted at the Family Planning Clinic/Metabolic Unit, University of Campinas, Brazil. Forty-eight women aged 18-39 years underwent HEC: 30 initiating use of DMPA and 18 initiating use of a copper intrauterine device (IUD). Data from 15 women in each group, who completed the follow-up and underwent HEC at12 months, were compared using repeated measures ANOVA. All women were advised to perform aerobic physical exercise for 150 min/week; body composition and total energy intake were evaluated. Main outcome measures were IR defined by M-value <4 mg/kg/min, and blood levels of insulin. Additional outcomes were total cholesterol, HDL-cholesterol, triglycerides, LDL-cholesterol, adipokines and free fatty acids.

RESULTS

At 12 months, two women in the DMPA group and none in the IUD group had developed IR. The groups were similar in in M-values and in blood levels of insulin, total cholesterol, HDL-cholesterol, LDL-cholesterol, adipokines or free fatty acids. Triglyceride levels increased in the DMPA group when compared to the IUD group, 80.0 (SD 47.8) versus 61.8 (SD 35.8) mg/dL respectively, (p=.033); and increased the total daily energy intake, 1828.3 (SD 518.9) versus 1300.8 (SD 403.4) kilocalories/24hs, respectively in the same groups, (p=.041). All the DMPA users showing higher insulin sensitivity at 12 months reported performing physical activity regularly.

CONCLUSIONS

Changes occurred in carbohydrate metabolism in DMPA users in the first year of use of the method. It is possible that the regular aerobic exercise may exert a beneficial and protective effect against the factors that trigger these changes.

IMPLICATIONS STATEMENT

Carbohydrate metabolism undergoes adverse changes in few young non-obese women during the first year of DMPA use and regular aerobic exercise may exert a beneficial and protective effect against these changes.

Progestogens used in postmenopausal hormone therapy: differences in their pharmacological properties, intracellular actions, and clinical effects

The safety of progestogens as a class has come under increased scrutiny after the publication of data from the Women's Health Initiative trial, particularly with respect to breast cancer and cardiovascular disease risk, despite the fact that only one progestogen, medroxyprogesterone acetate, was used in this study. Inconsistency in nomenclature has also caused confusion between synthetic progestogens, defined here by the term progestin, and natural progesterone. Although all progestogens by definition have progestational activity, they also have a divergent range of other properties that can translate to very different clinical effects. Endometrial protection is the primary reason for prescribing a progestogen concomitantly with postmenopausal estrogen therapy in women with a uterus, but several progestogens are known to have a range of other potentially beneficial effects, for example on the nervous and cardiovascular systems. Because women remain suspicious of the progestogen component of postmenopausal hormone therapy in the light of the Women's Health Initiative trial, practitioners should not ignore the potential benefits to their patients of some progestogens by considering them to be a single pharmacological class. There is a lack of understanding of the differences between progestins and progesterone and between individual progestins differing in their effects on the cardiovascular and nervous systems, the breast, and bone. This review elucidates the differences between the substantial number of individual progestogens employed in postmenopausal hormone therapy, including both progestins and progesterone. We conclude that these differences in chemical structure, metabolism, pharmacokinetics, affinity, potency, and efficacy via steroid receptors, intracellular action, and biological and clinical effects confirm the absence of a class effect of progestogens.

Differential regulation of endogenous pro-inflammatory cytokine genes by medroxyprogesterone acetate and norethisterone acetate in cell lines of the female genital tract

BACKGROUND

Medroxyprogesterone acetate (MPA) and norethisterone (NET) and its derivatives are widely used in female reproductive therapy, but little is known about their mechanisms of action via steroid receptors in the female genital tract. MPA used as a contraceptive has been implicated in effects on local immune function. However, the relative effects of progesterone (Prog), MPA and norethisterone acetate (NET-A) on cytokine gene expression in the female genital tract are unknown.

STUDY DESIGN

Using two epithelial cell lines generated from normal human vaginal (Vk2/E6E7) and ectocervical (Ect1/E6E7) cells as in vitro cell culture model systems for mucosal immunity of the female cervicovaginal environment, we investigated steroid receptor expression and activity as well as regulation of cytokine/chemokine genes by MPA and NET-A, as compared to the endogenous hormone Prog.

RESULTS

We show that the Prog, androgen, glucocorticoid and estrogen receptors (PR, AR, GR and ER, respectively) are expressed in both the Vk2/E6E7 and Ect1/E6E7 cell lines, and that the GR and AR are transcriptionally active. This study is the first to show ligand-, promoter- and cell-specific regulation of IL-6, IL-8 and RANTES (regulated-upon-activation, normal T cell expressed and secreted) gene expression by Prog, MPA and NET-A in these cell lines. Moreover, we show that the repression of the TNF-α-induced RANTES gene by MPA in the Ect1/E6E7 cell line is mediated by the AR.

CONCLUSION

Collectively, these data demonstrate that cell lines from different anatomical sites of the female genital tract respond differently to Prog and the synthetic progestins, most likely due to differential actions via different steroid receptors. The results highlight the importance of choice of progestins for immune function in the cervicovaginal environment. They further suggest that choice of progestins in endocrine therapy may have implications for women's risk of susceptibility to infections due to differential actions on genes involved in inflammation and immune function.

Molecular mechanisms of steroid receptor-mediated actions by synthetic progestins used in HRT and contraception

Synthetic progestins are used by millions of women as contraceptives and in hormone replacement therapy (HRT), although their molecular mechanisms of action are not well understood. The importance of investigating these mechanisms, as compared to those of progesterone, has been highlighted by clinical evidence showing that medroxyprogesterone acetate (MPA), a first generation progestin, increases the risk of breast cancer and coronary heart disease in HRT users. A diverse range of later generation progestins with varying structures and pharmacological properties is available for therapeutic use and it is becoming clear that different progestins elicit beneficial and adverse effects to different extents. These differences in biological activity are likely to be due to many factors including variations in dose, metabolism, pharmacokinetics, bioavailability, and regulation of, and/or binding, to serum-binding proteins and steroidogenic enzymes. Since the intracellular effects on gene expression and cell signaling of steroids are mediated via intracellular steroid receptors, differential actions via the progesterone and other steroid receptors and their isoforms, are likely to be the major cause of differential intracellular actions of progestins. Since many progestins bind not only to the progesterone receptor, but also to the glucocorticoid, androgen, mineralocorticoid, and possibly the estrogen receptors, it is plausible that synthetic progestins exert therapeutic actions as well as side-effects via some of these receptors. Here we review the molecular mechanisms of intracellular actions of old (MPA, norethisterone, levonorgestrel, gestodene) vs. new (drospirenone, dienogest, trimegestone) generation progestins, via steroid receptors.

Serum anti-müllerian hormone level is not altered in women using hormonal contraceptives

BACKGROUND

Anti-müllerian hormone (AMH) is secreted from granulosa cells of antral follicles into the circulation of adult women and hence could serve as an ovarian function test. This would be of value to hormonal contraceptive users if its serum level is unaffected by the use of hormonal contraceptives.

STUDY DESIGN

We prospectively recruited 95 women using combined oral contraceptive (n=23), combined injectable contraceptive (n=23), progestogen-only pills (n=9), progestogen-only injectable (n=20) and levonorgestrel intrauterine system (n=20), and measured their serum AMH concentration before and 3-4 months after treatment.

RESULTS

No significant difference in pre- and post-treatment serum AMH level was evident in all the treatment groups studied.

CONCLUSIONS

Being unaffected by hormonal contraceptives, serum AMH measurement is potentially a useful clinical test in hormonal contraceptive users for the differential diagnosis of anovulatory disorders and determination of menopause.

A possible role of progesterone receptor in mouse oocyte in vitro fertilization regulated by norethisterone and its reduced metabolite

BACKGROUND

The contraceptive effect of the progestogen norethisterone (NET) and its main metabolites 5alpha-NET and 3beta,5alpha-NET has been demonstrated in several species, and most studies have focused on the effects of these compounds in the uterus. We previously reported that 5alpha-NET inhibits the progesterone (P(4))-induced acrosome reaction in pig and mouse spermatozoa and induces severe morphological damage in two-cell fertilized mouse oocytes.

STUDY DESIGN

The main goal of this study was to analyze the possible role of P(4) receptor (PR) in the effects of NET and 5alpha-NET on the oocyte fertilization process. Different steroid treatments were used with or without cumulus-enclosed oocytes.

RESULTS

It was demonstrated that NET increases the percentage of fertilized oocytes in the same manner as P(4) does, while 5alpha-NET reduces the percentage of fertilized oocytes. This effect was not reversed by P(4) in the same concentrations.

CONCLUSION

A possible molecular mechanism for the effects of 5alpha-NET may be through a PR localized in the oocyte plasma membrane.

Usefulness of FSH measurements for determining menopause in long-term users of depot medroxyprogesterone acetate over 40 years of age

OBJECTIVE

To assess the usefulness of follicle-stimulating hormone (FSH) measurements for determining menopause in 40-55-year-old users of depot medroxyprogesterone acetate (DMPA).

STUDY DESIGN

FSH levels were measured in 355 blood samples from 82 amenorrheic women during an 18-month period. Blood was collected every 90 days immediately prior to DMPA administration.

RESULTS

Using FSH values>35 mIU/mL as being in the post menopausal range, 32 women (39.0%) presented at least one FSH measurement in the postmenopausal range and 14 of them (43.7%) had more than one elevated FSH measurement and were considered postmenopausal. In five users (15.6%), only the last FSH measurement was within the postmenopausal range, and in 13 women (40.6%), FSH returned to normal values following one measurement that was within the postmenopausal range.

CONCLUSIONS

The menopausal status in DMPA users in amenorrhea should be determined based on at least two consecutive high FSH evaluations, since, as shown here, 40.6% of the women with high FSH had a low FSH in the subsequent determination. FSH measurements should be done only in women>or=50 years old because there is a greater possibility of being in postmenopause. However, we do not recommend the interruption of DMPA use prior to the quantification of FSH.

Detection of raised FSH levels among older women using depomedroxyprogesterone acetate and norethisterone enanthate

The objective of this study was to investigate whether follicle-stimulating hormone (FSH) levels can be used reliably to indicate approaching menopause in older (aged 40-49), long-term users of depomedroxyprogesterone acetate (DMPA) and norethisterone enanthate (NET-EN). One-hundred and seventeen women using DMPA, 60 NET-EN users and 161 nonusers of contraception were recruited. At recruitment, serum FSH levels were measured and questions were asked regarding menopausal symptoms, menstrual cycle and date of last injection. Results of the recruitment blood test showed that 32% of the nonusers had FSH levels in the menopausal range >25.8 mIU/mL compared to 28% of the DMPA users and 9% of the NET-EN group. After adjusting for age, there was no significant difference between the 3 groups (p = 0.13). An increase of 1 year in age increased the FSH level by 3 mIU/mL (p < 0.001). All the hormonal contraceptive users were between 1 day and 12 weeks of their injection interval. Many had been using the injectable contraceptive method for over 10 years and almost all were amenorrheic at the time of recruitment. The data show that a raised FSH level can be detected during use of DMPA and NET-EN and could be used as a menopausal indicator without interrupting method use in this group of contraceptive users.

A-ring reduced metabolites of 19-nor synthetic progestins as subtype selective agonists for ER alpha

It has previously been demonstrated that 19-nor contraceptive progestins undergo in vivo and in vitro enzyme-mediated A-ring double bond hydrogenation. Bioconversion of 19-nor progestins to their corresponding tetrahydro derivatives results in the loss of progestational activity and acquisition of estrogenic activities and binding to the ER. Herein, we report subtype-selective differences in ligand binding and transcriptional potency of nonphenolic synthetic 19-nor derivatives between ER alpha and ER beta. In this study, we have examined both ER- and PR-mediated transcriptional activity of a number of A-ring chemically reduced derivatives of norethisterone and Gestodene. Double bond hydrogenation decreased the transcriptional potency of norethisterone and Gestodene through both PR isoforms with a 100- to 1,000-fold difference, respectively. In terms of the effects of norethisterone and Gestodene and their corresponding 5 alpha-dihydro (5 alpha-norethisterone and 5 alpha-Gestodene), or 3 alpha,5 alpha-tetrahydro or 3 beta,5 alpha-tetrahydro derivatives (3 alpha,5 alpha-norethisterone/3 alpha,5 alpha-Gestodene and 3 beta,5 alpha-norethisterone/3beta,5 alpha-Gestodene, respectively) on estrogen-mediated transcriptional regulation, the 3 beta,5 alpha-tetrahydro derivatives of both norethisterone and Gestodene showed the highest induction when HeLa cells were transiently transfected with an expression vector for ER alpha. This activity could be inhibited with tamoxifen. These compounds did not activate gene transcription via ER beta, and none of them showed antagonistic activities through either ER subtype. The 3 beta,5 alpha-tetrahydro derivatives of both norethisterone and Gestodene were active in other cells in addition to HeLa cells and activated reporter expression through the oxytocin promoter. In summary, two ER alpha selective agonists have been identified. These compounds, with ER alpha vs. ER beta selective agonist activity, may be useful in evaluating the distinct role of these receptors as well as in providing useful insights into ER action.

Differential effects of 5 alpha-norethisterone on the histomorphology of the oviduct and uterus of the pregnant rabbit

In this study, the histomorphological changes induced by 5 alpha-norethisterone (5 alpha-NET), a reduced metabolite of the contragestational postcoital agent norethisterone, in the oviduct and the uterus of the pregnant rabbit were determined. Adult fertilized rabbits were treated daily with 5 alpha-NET (1.0, 1.5, 2.5, and 5.0 mg/kg/day) during 7 consecutive days, starting from the first day after coitus. Twenty-four hours after the last administration, the histological analysis of the oviduct and the uterus was performed. It was observed that in the infundibulum-ampullae region as well as in the isthmus of the oviduct, the number of nonsecretory cells (PAS-negative) were decreased, whereas the number of secretory cells (PAS-positive) were increased significantly after 5 alpha-NET administration. The proportion of glandular tissue in the uterus markedly diminished in relation to that of the stromal tissue. This indicates an inhibition of the endometrial transformation observed during normal pregnancy. Interestingly, the highest doses of 5 alpha-NET (2.5 and 5.0 mg/kg/day) induced necrosis in the uterus but not in the oviduct. These results suggest that the molecular antiprogestational effects previously observed after 5 alpha-NET administration are also related to changes in the histomorphology of both the oviduct and the uterus of the pregnant rabbit.

Mechanisms of hormonal and antihormonal action of contraceptive progestins at the molecular level

19-Nor synthetic progestins undergo extensive metabolism at the target cells. The resulting metabolic conversion products interact with putative steroid receptors within the cells, and through those interactions, they may exert either agonistic, synergistic and antagonistic hormonal effects. Studies conducted in our laboratories have disclosed that norethisterone (NET) and D-(1) norgestrel (LNG), two widely used contraceptive progestins, are biotransformed to several A-ring reduced (dihydro and tetrahydro) derivatives. The resulting metabolites 5 alpha-dihydro NET (5 alpha-NET) and 5 alpha-dihydro LNG bind with relative high affinity to the progesterone and androgen receptors. To gain insight into the underlying molecular events mediating the mode of action of NET and its neutral metabolites, we have examined the expression of their biological effects at target organs by using the rabbit uteroglobin gene model and the beta-glucuronidase activity of the mouse kidney. The results of a series of experiments seem to indicate that the enzyme-mediated formation of the 5 alpha (trans A/B ring junction) NET derivative results in a significant diminution of its progestational and androgenic potencies. Furthermore, 5 alpha-NET acquire a potent anti-progestational/contragestational effect as assessed in the female rabbit. These results demonstrated that 5 alpha-reduction of 19-nor progestins exerts a paradoxical effect, at least in terms of their hormone-like effects. The overall data are in line with the concept that metabolism of synthetic progestins at hormone-sensitive organs modulates their mechanisms of action.

Induction of male sexual behavior by norethisterone: role of its A-ring reduced metabolites

The estrogenic and androgenic potencies of norethisterone (NET), a synthetic nonaromatizable progestin, and three of its reduced metabolites (5 alpha-NET; 3 alpha, 5 alpha-NET; 3 beta, 5 alpha-NET) were assessed by their ability to restore male sexual behavior in castrated male rats following their chronic administration in combination with either 5 alpha-dihydrotestosterone (DHT) or estradiol (E2), or when given alone. Full restoration of mating was achieved when 3 beta, 5 alpha-NET was administered with DHT, indicating an estrogenic effect of this compound. Lower estrogenic effects were noticed with 3 alpha, 5 alpha-NET and 5 alpha-NET, while NET had very little estrogenic potency. The only effective compound to restore ejaculation, when administered with E2, was NET, indicating its androgen-like intrinsic potency. When administered alone, NET exerted the most potent effect on male behavior, followed by 5 alpha-NET, while the tetrahydro derivatives were ineffective. The observation that NET alone restored male sexual activity at a level identical to that induced by testosterone demonstrated an androgenic-estrogenic activity of this progestin exerted through its intrinsic androgenic effect, and the estrogenic effect of its tetrahydro derivatives. Overall results indicated that the metabolism of NET modulates its mode of action at the brain, and support the concept that both estrogenic and androgenic effects are required for mating activation.

Interactions between estrogens, androgens, progestins, and glucocorticoids in ZR-75-1 human breast cancer cells

The human breast cancer cell line ZR-75-1 possesses androgen, estrogen, progesterone, and glucocorticoid receptors, thus offering a good model to study the specific role of each class of steroids in the control of breast cancer growth. Although the stimulatory action of classical estrogens (E2 and estrone) is well known, we have found a potent mitogenic effect of the adrenal estrogen androst-5-ene-3 beta,17 beta-diol (delta 5-diol) at concentrations within the range of those found in the serum of adult women, thus suggesting that delta 5-diol might be the most important estrogen in women. Androgens, on the other hand, exert a potent inhibitory effect on basal ZR-75-1 cell growth and completely reverse the stimulatory effect of estrogens on the same parameter. The antiproliferative effect of androgens was completely prevented by the antiandrogen OH-FLU, thus suggesting an action mediated by the androgen receptor. Part of the effect of androgens can be explained by the marked inhibition of estrogen receptor binding and mRNA levels by androgens. The antiproliferative effect of androgens is additive to that exerted by antiestrogens. Progestins, on the other hand, exert a specific antiproliferative effect in the presence of estrogens, the effect of progestins being antagonized by the stimulatory action of insulin on cell growth. Medroxyprogesterone acetate (MPA), a compound frequently used in the treatment of breast cancer in women, exerts its main inhibitory action through an androgen receptor-mediated action, whereas its glucocorticoid-like activity could play an additional role at high concentrations. All four classes of steroids are present, to various extents, as lipophilic esters of long-chain fatty acids. It is of interest to mention that all steroids that inhibit ZR-75-1 breast cancer cell growth (androgens, progestins, and glucocorticoids) stimulate the secretion and mRNA levels of gross cystic disease fluid protein-15 (GCDFP-15), whereas estrogens have the opposite effects, thus suggesting that GCDFP-15 could well be a good marker for monitoring the response to androgens, progestins, and antiestrogens during the course of breast cancer therapy.

Androgen and glucocorticoid receptor-mediated inhibition of cell proliferation by medroxyprogesterone acetate in ZR-75-1 human breast cancer cells

Medroxyprogesterone acetate (MPA) is a synthetic progestin, currently used in the adjuvant treatment of advanced breast cancer, which induces remission rates (30-40%) comparable to those obtained with other types of endocrine therapies. Since, in addition to its progestin-like action, MPA exhibits androgen- and glucocorticoid-like activities in other tissues, the present study was designed to assess the relative contribution of the different steroid receptor systems in the direct action of MPA on breast cancer cell growth, using the ZR-75-1 human mammary carcinoma cell line as an in vitro model. Unlike pure progestins, MPA potently inhibited the proliferation of ZR-75-1 cells in a concentration-dependent manner either in the presence or in the absence of estrogens, and the addition of insulin had only marginal effects on its growth-inhibitory activity. On the other hand, both hydroxyflutamide (OHF, a non-steroidal monospecific antiandrogen) and RU486 (a potent antiglucocorticoid and antiprogestin also endowed with antiandrogenic activity) competitively reversed MPA antiproliferative effects. MPA further decreased the growth of ZR-75-1 cells co-incubated with maximally inhibitory concentrations of either 5 alpha-dihydrotestosterone (DHT) or dexamethasone (DEX), although at about 300-fold higher MPA concentrations with DHT-treated than with DEX-treated ZR-75-1 cells, thus demonstrating a highly predominant androgenic effect. However, MPA had no effect on the growth of ZR-75-1 cells co-incubated with DHT and DEX simultaneously, thus supporting the predominant role of androgen and glucocorticoid receptors in MPA action. A 12-day preincubation of ZR-75-1 cells with increasing concentrations of MPA (10(-12) to 3 x 10(-6)M) decreased the specific uptake of [3H]estradiol (E2) by intact cell monolayers to the same extent as 10 nM DHT, an effect which was competitively blocked by the addition of OHF (3 microM). MPA action on ZR-75-1 cell growth also significantly differed from that of progestins in being additive to the inhibition of E2-stimulated growth by the steroidal antiestrogen ICI164384. The present data indicate that the main action of MPA on ZR-75-1 human breast cancer cell growth is due to its androgen receptor-mediated inhibitory action, while its glucocorticoid-like activity could play an additional role at high concentrations.

Medroxyprogesterone acetate: receptor binding and correlated effects on steroidogenesis in rat granulosa cells

Medroxyprogesterone acetate (MPA), a widely used synthetic steroid, was studied to determine both its effects on steroid receptors and steroidogenesis in the well-characterized rat ovarian granulosa cell model. Initial receptor binding studies showed MPA was as potent as progesterone and 10-fold less potent than R-5020 (an active synthetic progestin) in binding to progesterone cytosolic receptors in rat ovarian granulosa cells. MPA was 20-fold less potent than testosterone, and 10-fold less potent than dexamethasone in binding to the androgen and glucocorticoid cytosolic receptors, respectively. The binding of MPA to progestrone, androgen and glucocorticoid receptors predicted direct effects of MPA on FSH-stimulated estrogen (E), progesterone (P), and 20 alpha-dihydroprogesterone (DHP) production by cultured rat ovarian granulosa cells. MPA at 10(-7) to 10(-6) M significantly augmented FSH-stimulated P and DHP production (a previously documented progestin, androgen and glucocorticoid effect). This augmentation was blocked by the concurrent addition to cell culture of 10-fold excess RU-486 (a potent anti-progestin and anti-glucocorticoid). At concentrations greater than 10(-6) M, MPA inhibited the production of P and DHP (a progestin effect), and the production of E (a progestin and glucocorticoid effect). MPA, structurally a progestin, has complex steroid hormone effects predicted by its interaction with progesterone, androgen and glucocorticoid receptors.

Steroid analogs inhibit hormone binding by an extract from Nippostrongylus brasiliensis (Nematoda)

1. An extract from the rodent nematode Nippostrongylus brasiliensis contained putative receptors that bound radiolabeled sex hormones, based on isoelectric focusing. 2. Binding of radiolabeled testosterone by receptors at pH 4.4 was highly inhibited by the androgen analogs, testosterone-3-oxime and 4-aza-5-androsten-3-on-17 beta-ol. 3. Binding of radiolabeled progesterone by receptors at pH 6.4 was highly inhibited by the progesterone analogs 3,5-seco-4-norpregnan-5-on-3-oic acid and 19-norethisterone or 21-deoxycorticosterone. 4. Binding of radiolabeled 17 beta-estradiol by receptors at pH 4.9 was highly inhibited by epiandrosterone. 5. In vivo development of N. brasiliensis to the adult was partially inhibited by selected steroid analogs.

The metabolism of 19-nor contraceptive progestins modulates their biological activity at the neuroendocrine level

In this communication, a series of studies from our laboratory dealing with the mechanism of action of 17 alpha-ethinyl derivatives of 19-nor testosterone are reviewed. The administration of norethisterone (NET) to long-term castrated female rats induces the nuclear translocation of pituitary estradiol receptors and is followed by some estrogenic-like effects at the hypothalamic-pituitary unit. It is established that an A-ring reduced metabolite of NET, the 3 beta,5 alpha-tetrahydro NET derivative, is responsible for the observed in vivo estrogenic effects of the parent compound. 3 beta,5 alpha-NET binds to the estrogen receptor and is efficient in inducing the pituitary estrogen-dependent progesterone receptor and in increasing the uterine weight in long-term castrated rats. Furthermore, administration of 3 beta,5 alpha-NET and the 5 alpha-reduced metabolite of NET (5 alpha-NET) are able to inhibit the release of gonadotropins in the castrated animal to a greater extent than NET. Moreover, pretreatment with tamoxifen, an estrogen binding site competitor, results in a significant diminution of the antigonadotropic potency of 3 beta,5 alpha-NET but not of the 5 alpha-NET, which is only inhibited by the administration of cyproterone acetate. These findings underline the importance of the metabolic rate of NET for the expression of its biological effects at the hypothalamic-pituitary unit.

Stereospecificity of the intracellular binding of norethisterone and its A-ring reduced metabolites

The interaction of norethisterone (NET) and four A-ring reduced metabolites of NET with cytosol receptors for progesterone (PR), androgen (AR), and estrogen (ER) was investigated. Cytosol preparations from: uteri of adult estrogen-primed castrated rats, ventral prostates of adult castrated rats and uteri of immature rats were used as the source of PR, AR, and ER respectively. 3H-Labeled ORG-2058, R-1881, and 17 beta-estradiol were used as the radioligands. The results of competitive studies disclosed that: the most efficient competitor for PR binding sites was NET (Ki = 1.1 X 10(-7) M) followed by 5 alpha-dihydro NET (5 alpha-NET), whereas the 3 alpha,5 alpha; 3 beta,5 alpha and 3 alpha,5 beta-tetrahydro NET derivatives were ineffective the most efficient competitor for AR binding sites was 5 alpha-NET (Ki = 1 X 10(-8), immediately followed by NET, while the three tetrahydro NET derivatives were not competitors and remarkable competition for ER binding sites was only exhibited by the 3 beta,5 alpha-tetrahydro NET derivative (Ki = 4.6 X 10(-8) M) and to a lesser extent by its 3 alpha,5 alpha-epimeric alcohol, while NET and 5 alpha-NET were completely ineffective. These findings demonstrate the stereospecificity of the intracellular binding of NET and its reduced metabolites with cytosol steroid putative receptors, and provide biochemical support to the understanding of the variety of hormone-like effects observed after the in vivo administration of NET.

Steroid modulation of Mullerian duct regression in the chick embryo

The recent demonstrations that Mullerian inhibiting substance (MIS) is present in embryonic chick ovaries (P. K. Hutson, H. Ikawa, and P. K. Donahoe (1981). J. Pediatr. Surg. 16, 822-827), and that exogenous diethylstilbestrol does not significantly inhibit MIS secretion from feminized testes (Hutson et al. (1982) J. Pediatr. Surg. 17, 953-959), suggest that ovarian estrogens protect the female left Mullerian duct from MIS-induced regression. The possibility exists, however, that ovarian MIS may be inactive. This study was designed to see if interference with estrogen action in ovo would allow MIS to cause regression of the female left Mullerian duct. The "antiestrogens," tamoxifen and LY117018, had little effect on the female Mullerian ducts unless given in high doses or with added testosterone (greater than 0.1 mg). Two compounds known to inhibit estrogen synthesis, aminoglutethimide and 4-hydroxyandrostenedione, had no effect on their own, even in high doses (less than 1.0 mg/egg). However, when administered together (0.5 mg each) there was significant disappearance of the lower ends of both Mullerian ducts. Norethindrone, which has been described recently as an aromatase inhibitor (Y. Osawa, C. Yarborough, and V. Osawa (1982). Science (Washington, D. C.) 215, 1249-1251) caused partial regression of the upper end of the left Mullerian duct as well as complete loss of the lower ends of both ducts in the female. These results suggest that the steroid environment is a critical factor in the response of the Mullerian ducts to MIS, and that estrogen blockage may allow endogenous MIS from the ovary to induce partial regression of the Mullerian ducts in the female chick embryo.

Steroid hormone receptors in normal and malignant human renal tissue: relationship with progestin therapy

Documented hormone dependence of renal tumors in animal models, hypothetical hormonal environment of human kidney neoplasms and their controversial response to endocrine therapy prompted us to undertake a prospective multicentric cooperative study to evaluate the hormone-dependence/responsiveness of renal tumors. Patients with renal carcinoma were stratified according to the TNM classification and after nephrectomy were treated with high-dose medroxyprogesterone acetate (MPA). Specimens of tumor and healthy surrounding kidney tissue were studied for titration of steroid receptor proteins (78 for androgen, AR, 89 for estrogen, ER, and progestin, PgR). Their true receptor nature was estimated. Very low titers (on an average less than 10 fmol/mg protein) were found, especially for ER and PgR in neoplastic samples. Occurrence rate of AR was low for both tissues (less than 20%), whereas ER and PgR were detected at a higher frequency in healthy parenchyma than in tumor tissue (42.2 vs 23.3% and 30.7 vs 11.2%, respectively). AR was moderately affected by metastatic status of the disease and by sex. All three steroid receptors were simultaneously detected in normal tissue in 11.7% of cases and in tumor tissue in only 3.8%. No significant correlation between receptor status in the tumor and clinical response to hormone therapy was found. In 27 cases who received adjuvant MPA therapy, relapses were respectively 43.8 and 18.2% in the patients with negative receptors or with at least one detectable receptor. In metastatic renal carcinoma, stabilization of the disease with MPA was achieved more frequently in receptor-negative patients. Therefore, we conclude that the receptor assay is not a valid tool to select renal carcinoma patients for therapy with MPA.

Nuclear translocation of estradiol receptors by the in vivo administration of norethisterone: an alternate mechanism for gonadotropin inhibition

In order to investigate the anti-gonadotropic effect of norethisterone (NET) in long-term ovariectomized rats, we studied the interaction of this synthetic progestin with intracellular steroid receptors in the anterior pituitary by a nuclear exchange assay. The results demonstrated that the administration of NET to long-term ovariectomized rats resulted in nuclear translocation of estradiol cytosol receptors in the pituitary and uterus with a rate of accumulation and nuclear retention being similar in both tissues. Accumulation of nuclear estradiol receptors in the pituitary was in agreement with the rate of LH inhibition in NET-treated rats. The results presented in this communication may explain the anti-gonadotropic activity of NET in long-term ovariectomized rats in addition to its well known progestational activity.

Interaction of medroxyprogesterone acetate with cytosol androgen receptors in the rat hypothalamus and pituitary

The binding of medroxyprogesterone acetate (MPA) with cytosol androgen receptors from rat pituitary and hypothalamus was studied. The pituitary and hypothalamic cytosol androgen receptors from adult castrated female rats were in vitro labeled using 3H natural (testosterone (T) and 5 alpha-dihydrotestosterone (DHT] and [3H]synthetic (methyltrienolone) androgens as radioligands. The [3H]androgen-receptor complexes sedimented with a coefficient of 8S in linear sucrose gradients. When incubated with an excess of radioinert MPA, specific binding was abolished indicating interaction of MPA with androgen receptors. Furthermore specific [3H]MPA-androgen cytosol receptor complexes could be identified in these neuroendocrine tissues when a post-gradient receptor labeling technique was used in the absence or presence of radioinert MPA, DHT, and triamcinolone acetonide. A study of binding kinetics disclosed that the equilibrium dissociation constant and saturation binding capacity for the MPA binder, were similar to those exhibited by DHT binding to androgen receptors in both studied tissues under identical experimental conditions. The overall results were interpreted as demonstrating that MPA interacts with cytosol steroid receptors other than those of progesterone in the rat hypothalamus and anterior pituitary. The data are consistent with MPA binding to androgen receptors.

Effects of synthetic steroid contraceptives on biliary lipid composition of normal Mexican women

The effects of two hormonal contraceptives upon the biliary lipid composition of Mexican women were evaluated in a prospective study. Twenty-one healthy volunteers of reproductive age were allocated into three groups (7 subjects each). Group I served as the experimental control (all subjects were bearing a non-medicated IUD), group II received i.m. norethisterone enanthate (NET-e) 200 mg every two months, and group III received an oral combination of 1-norgestrel 150 micrograms and ethinyl estradiol 30 micrograms. The bile lithogenic index as assessed by the relative proportion of cholesterol to bile acids and lecithin was determined in duodenal bile samples obtained before (baseline), during (4 months), and after (12 months) contraceptive administration. The results indicated that NET-e administration resulted in a slight although significant increase of the lithogenic index while the oral formulation did not. The overall data were interpreted as demonstrating that administration of these steroid contraceptives does not constitute a risk factor in terms of gallstone formation in the population studied. The estrogen-like behavior exhibited by NET-e is discussed.

Progestins can mimic, inhibit and potentiate the actions of androgens

There is an extensive background on the androgen responsiveness of the mouse kidney which can be demonstrated histologically by hypertrophy of the Bowman's capsule and the proximal convoluted tubule. Although androgens increase many renal proteins, beta-glucuronidase and ODC are distinguished by exquisite genetic regulation of the magnitude of the response induced by testosterone. Both the qualitative and quantitative expression of the genes for these enzymes are strain specific, and are dependent upon regulatory alleles. Ornithine decarboxylase is of particular interest since the response of this enzyme is rapid compared to that of beta-glucuronidase. Recent studies using a newly developed androgen receptor assay have demonstrated that the duration of retention of the androgen receptor complex in the nucleus correlates with the magnitude of the androgenic response. Progestins can mimic, inhibit, or potentiate the action of androgens. These responses have been termed the androgenic, antiandrogenic and synandrogenic actions of progestins, respectively. The androgenic and antiandrogenic action of this class of steroids are manifest on many tissues and on many endpoints within a given organ. These effects are believed to involve an early step(s) of androgen action which is common to all sensitive tissues. Results to date suggests that this early step involves the androgen receptor. By contrast, the synandrogenic action of progestins is limited in that it is not observed on all tissues, and not even on all endpoints within a single organ. In the mouse kidney, the synandrogenic actions of progestins have been most extensively studied on beta-glucuronidase. With this enzyme this unusual response to progestins can be demonstrated only in mice which carry the Gus-ra allele. This observation suggests that the potentiating action of progestins on beta-glucuronidase is manifest directly on the Gus gene complex. It is not certain at this time whether a similar mechanism is involved in the potentiation of androgen action on other organs such as the prostate. The androgenic action of progestins is believed to be similar to that of other androgens. Androgenic progestins such as MPA bind to the androgen receptors and translocate them to nuclei. This is followed by a dose dependent increase of proteins similar to what is observed after testosterone administration. In addition, the regulatory genes which modulate androgen action have the same effect on the androgenic effect of progestins. The fact that the potency of progestins such as MPA is less than that of testosterone is believed to relate in part to their lower affinity for the androgen receptors.(ABSTRACT TRUNCATED AT 400 WORDS)