Effect of dehydroepiandrosterone on vaginal and uterine histomorphology in the rat

Revisiting the physiological role of androgens in women

INTRODUCTION

Extensive research underlines the critical functions of androgens in females. Nevertheless, the precise mechanisms of their action are poorly understood. Here, we review the existing literature regarding the physiological role of androgens in women throughout life.

AREAS COVERED

Several studies show that androgen receptors (ARs) are broadly expressed in numerous female tissues. They are essential for many physiological processes, including reproductive, sexual, cardiovascular, bone, muscle, and brain health. They are also involved in adipose tissue and liver function. Androgen levels change with the menstrual cycle and decrease in the first decades of life, independently of menopause.

EXPERT OPINION

To date, studies are limited by including small numbers of women, the difficulty of dosing androgens, and their cyclical variations. In particular, whether androgens play any significant role in regulating the establishment of pregnancy is poorly understood. The neural functions of ARs have also been investigated less thoroughly, although it is expressed at high levels in brain structures. Moreover, the mechanism underlying the decline of dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) with age is unclear. Other factors, including estrogen's effect on adrenal androgen production, reciprocal regulation of ARs, and non-classical effects of androgens, remain to be determined.

Understanding sexual arousal and subjective-genital arousal desynchrony in women

Sexual arousal in women comprises two components: genital arousal and subjective arousal. Genital arousal is characterized by genital vasocongestion and other physiological changes that occur in response to sexual stimuli, whereas subjective arousal refers to mental engagement during sexual activity. For some women, genital arousal enhances subjective arousal; for others, the two types of arousal are desynchronous. However, the relationship between genital and subjective arousal might not be relevant to the diagnosis and treatment of sexual arousal dysfunction. Studies have shown that not all women who report sexual arousal problems have decreased genital arousal, and only some women with decreased genital arousal have low subjective arousal. To develop efficacious treatments for female sexual arousal dysfunction, researchers need to differentiate the women for whom genital sensations have a critical role in their subjective arousal from those who are not mentally aroused by genital cues. The mechanisms by which women become aroused and the inputs into arousal have considerable implications for treatment outcomes.

Treatment of moderate to severe dyspareunia with intravaginal prasterone therapy: a review

The loss of sex steroids (e.g. estradiol, dehydroepiandrosterone [DHEA], progesterone) that causes menopause commonly affects a woman's general health and produces bothersome physical changes that may interfere with normal sexual and genitourinary functioning. Although both over-the-counter and prescription treatments are available, there remains a large unmet need, as less than 10% of women are treated. Adrenal DHEA and its sulfate are the most abundant steroids in humans. Here we review the development of intravaginal prasterone, the synthetic equivalent to endogenous DHEA. Prasterone is approved by the US Food and Drug Administration for the treatment of moderate to severe dyspareunia, a symptom of vulvar and vaginal atrophy, due to menopause. Prasterone has been shown to decrease the pain associated with dyspareunia, and to improve vaginal pH, as well as superficial and parabasal cell counts, while maintaining serum hormone levels within the range of those seen in normal postmenopausal women. Unlike other menopausal prescription therapies, intravaginal prasterone does not carry a boxed warning, thus allowing the clinician and patient to engage in meaningful and reassuring discussion around a new approach that treats this common, debilitating condition.

Combined data of intravaginal prasterone against vulvovaginal atrophy of menopause

OBJECTIVE

To analyze the effects of intravaginal prasterone obtained in the three randomized clinical studies performed in postmenopausal women suffering from moderate to severe (MS) dyspareunia due to vulvovaginal atrophy (VVA).

METHODS

In three independent 12-week prospective, randomized, double-blind, and placebo-controlled clinical studies, the effect of daily intravaginal 0.50% (6.5 mg) prasterone was examined on four co-primary objectives in women having MS pain during sexual activity (dyspareunia), identified as their most bothersome symptom (MBS) of VVA at baseline.

RESULTS

In 436 women treated with 0.50% prasterone and 260 women who received placebo, an average 35.1% decrease over placebo in the percentage of parabasal cells (P < 0.0001), an average 7.7% increase in the percentage of superficial cells (P < 0.0001), and a mean 0.72 pH unit decrease in vaginal pH (P < 0.0001) were observed. The severity score of most bothersome symptom dyspareunia was decreased by a 0.46 unit (49%) (P < 0.0001 over placebo), whereas the severity score of MS vaginal dryness decreased by 0.31 unit (P < 0.0001 over placebo). A very positive evaluation was obtained on the acceptability of the technique of administration of the insert, whereas the male partners reported a very positive evaluation of the changes observed in their sexual partner.

CONCLUSION

The efficacy data demonstrate highly positive effects on all the symptoms and signs of vulvovaginal atrophy with no significant drug-related side effects in line with the physiology of menopause and intracrinology.

Role of Androgens in Female Genitourinary Tissue Structure and Function: Implications in the Genitourinary Syndrome of Menopause

INTRODUCTION

Genitourinary conditions in women increase in prevalence with age. Androgens are prerequisite hormones of estrogen biosynthesis, are produced in larger amounts than estrogens in women, and decrease throughout adulthood. However, research and treatment for genitourinary complaints have traditionally focused on estrogens to the exclusion of other potential hormonal influences.

AIM

To summarize and evaluate the evidence that androgens are important for maintaining genitourinary health in women and that lack of androgenic activity can contribute to the development of symptoms of the genitourinary syndrome of menopause.

METHODS

The role of androgens in the pathophysiology, diagnosis, and treatment of genitourinary syndrome of menopause was discussed by an international and multidisciplinary panel during a consensus conference organized by the International Society for the Study of Women's Sexual Health. A subgroup further examined publications from the PubMed database, giving preference to clinical studies or to basic science studies in human tissues.

MAIN OUTCOME MEASURES

Expert opinion evaluating trophic and functional effects of androgens, their differences from estrogenic effects, and regulation of androgen and estrogen receptor expression in female genitourinary tissues.

RESULTS

Androgen receptors have been detected throughout the genitourinary system using immunohistochemical, western blot, ligand binding, and gene expression analyses. Lower circulating testosterone and estradiol concentrations and various genitourinary conditions have been associated with differential expression of androgen and estrogen receptors. Supplementation of androgen and/or estrogen in postmenopausal women (local administration) or in ovariectomized animals (systemic administration) induces tissue-specific responses that include changes in androgen and estrogen receptor expression, cell growth, mucin production, collagen turnover, increased perfusion, and neurotransmitter synthesis.

CONCLUSION

Androgens contribute to the maintenance of genitourinary tissue structure and function. The effects of androgens can be distinct from those of estrogens or can complement estrogenic action. Androgen-mediated processes might be involved in the full or partial resolution of genitourinary syndrome of menopause symptoms in women. Traish AM, Vignozzi L, Simon JA, et al. Role of Androgens in Female Genitourinary Tissue Structure and Function: Implications in the Genitourinary Syndrome of Menopause. Sex Med Rev 2018;6:558-571.

Science of intracrinology in postmenopausal women

OBJECTIVE

To illustrate the marked differences between classical endocrinology that distributes hormones to all tissues of the body through the bloodstream and the science of intracrinology, whereby each cell of each peripheral tissue makes a small and appropriate amount of estrogens and androgens from the inactive precursor dehydroepiandrosterone (DHEA), DHEA being mainly of adrenal origin. Because only the inactivated sex steroids are released in the blood, influence in the other tissues is avoided.

METHODS

Molecular biology has been used for the identification/characterization of the steroid-forming and steroid-inactivating enzymes, whereas steroids have been measured by mass spectrometry-based assays validated according to the US Food and Drug Administration guidelines.

RESULTS

Evolution over 500 million years has engineered the expression of about 30 steroid-forming enzymes specific for each peripheral tissue. These tissue-specific enzymes transform DHEA into the appropriate small amounts of estrogens and androgens for a strictly intracellular and local action. Humans, contrary to species below primates, also possess intracellular steroid-inactivating enzymes, especially glucuronyl transferases and sulfotransferases, which inactivate the estrogens and androgens at their local site of formation, thus preventing the release of a biologically significant amount of estradiol (E2) and testosterone in the circulation. Since DHEA becomes the unique source of sex steroids after menopause, serum E2 and testosterone are thus maintained at low biologically inactive concentrations with no activity outside the cells of origin. DHEA secretion, unfortunately, starts decreasing at about the age of 30 at various rates in different women. Moreover, there is no feedback mechanism to increase DHEA secretion when the concentration of serum DHEA decreases. Considering this mechanism is unique to the human, it seems logical to replace DHEA locally in women suffering from vulvovaginal atrophy (genitourinary syndrome of menopause). The clinical data obtained using a small dose of intravaginal DHEA (prasterone) confirm the mechanisms of intracrinology mentioned above which avoid biologically significant changes in serum E2 and testosterone.

CONCLUSIONS

The symptoms and signs of vulvovaginal atrophy (genitourinary syndrome of menopause) can be successfully treated by the intravaginal administration of DHEA without safety concerns. This strategy exclusively replaces in the vagina the missing cell-specific intracellular estrogens and androgens. This approach avoids systemic exposure and the potential risks of estrogen exposure for the tissues other than the vagina.

Comparison of intravaginal 6.5mg (0.50%) prasterone, 0.3mg conjugated estrogens and 10μg estradiol on symptoms of vulvovaginal atrophy

The objective is to compare the effect of intravaginal dehydroepiandrosterone (DHEA, prasterone), conjugated equine estrogens (CEE) and estradiol (E₂) on moderate to severe dyspareunia and/or vaginal dryness. In a review of available data, independent prospective, randomized, double-blind and placebo-controlled Phase III 12-week clinical trials involved daily administration of 6.5mg (0.50%) prasterone, daily (21days on/7days off) 0.3mg CEE, twice weekly 0.3mg CEE or 10μg E₂ daily for 2 weeks followed by twice weekly for 10 weeks. Vulvovaginal atrophy (VVA) symptoms were evaluated by questionnaires. The total severity score of dyspareunia decreased from baseline by 1.27 to 1.63 units with prasterone treatment, 1.4 with CEE and 1.23 in one statistically significant study with E₂ (combined symptoms). Decreases over placebo ranged from 0.35 to 1.21 with prasterone, 0.7 to 1.0 with CEE and 0.33 for the E₂ study. The total decreases in vaginal dryness severity ranged from 1.44 to 1.58 units for prasterone, 1.1 unit for CEE and 1.23 unit for E₂. The decreases over placebo of vaginal dryness intensity ranged from 0.30 to 0.43 unit for prasterone, 0.40 unit for CEE and 0.33 for the E₂ study with combined symptoms. Daily 6.5mg (0.50%) prasterone appears to be at least as efficacious as 0.3mg CEE or 10μg E₂ for treatment of the VVA symptoms. In summary, the beneficial effects on the VVA symptomatology can be obtained by the addition of a small amount of intravaginal prasterone to compensate for the low serum concentration of prasterone observed in the majority of women after menopause without concerns about systemic effects.

Androgens in women are essentially made from DHEA in each peripheral tissue according to intracrinology

The objective is to review how the cell-specific amounts of intracellular androgens are all made in women from circulating dehydroepiandrosterone (DHEA) in each peripheral tissue, independently from the rest of the body. Following 500 million years of evolution, approximately three dozen cell-specific intracrine enzymes have been engineered in human peripheral tissues whereby the inactive sex steroid precursor DHEA mainly of adrenal origin is transformed into the appropriate minute intracellular amounts of androgens. These intracellular androgens are inactivated in the same cells, with no biologically significant release of active androgens in the circulation. The best estimate is that approximately 50% as much androgens are synthesized in women, compared to men of the same age. The problem with DHEA, however, the exclusive source of androgens in women of all ages, is that DHEA secretion has already decreased by an average of 60% at time of menopause and continues to decrease thereafter. The human-specific and highly sophisticated mechanisms of intracrinology permit each cell to control androgen availability according to its own needs independently from the remaining of the body. Such a mechanism is completely different from classical endocrinology well understood in men where testosterone of testicular origin is transported through the blood and has indiscriminate access to the androgen receptor (AR) in all AR-containing cells of the body. In men, both the endocrine and intracrine mechanisms are in operation while, in women, only the intracrine mechanisms responsible for intracellular formation from DHEA provide androgens.

The Rat Mammary Gland: Morphologic Changes as an Indicator of Systemic Hormonal Perturbations Induced by Xenobiotics

The development and morphology of the rat mammary gland are dependent upon several hormones including estrogens, androgens, progesterone, growth hormone and prolactin. In toxicology studies, treatment with xenobiotics may alter these hormones resulting in changes in the morphology of reproductive tissues such as the mammary gland. In the rat, male and female mammary glands exhibit striking morphologic differences that can be altered secondary to hormonal perturbations. Recognizing these morphologic changes can help the pathologist predict potential xenobiotic-induced perturbations in the systemic hormonal milieu. This review examines the development of the rat mammary gland and the influence of sex hormones on the morphology of the adult male and female rat mammary gland. Specific case examples from the literature and data from our laboratory highlight the dynamic nature of the rat mammary gland in response to hormonal changes.

Role of androgens in modulating male and female sexual function

Advancement in basic and clinical research has provided considerable evidence suggesting a key role of androgens in the physiology and pathophysiology of sexual function. Evidence from clinical studies in men and women with androgen deficiency support a role of androgens in maintaining sexual function in men and women and are integral in maintaining sexual health. Preclinical studies utilizing male animal models demonstrated a role of androgens in maintenance of: (i) penile tissue structural integrity, (ii) penile trabecular smooth muscle growth and function, (iii) integrity of penile nerve fiber network, (iv) signaling pathways in the corpora cavernosa, (v) myogenic and adipogenic differentiation in the corpora cavernosa, (vi) physiological penile response to stimuli, and (vii) facilitating corporeal hemodynamics. These findings strongly suggest a role for androgen in the physiology of penile erection. In addition, clinical studies in hypogonadal men with erectile dysfunction treated with testosterone provided invaluable information on restoring erectile function and improving ejaculatory function. Similarly, clinical studies in surgically or naturally postmenopausal women with androgen deficiency suggested that androgens are important for maintaining sexual desire and testosterone treatment was shown to improve sexual desire, arousal and orgasm. Furthermore, studies in female animal models demonstrated that androgens maintain the integrity of vaginal nerve fiber network, muscularis volume, and enhance genital blood flow and mucification. Based on the biochemical, physiological and clinical findings from human and animal studies, we suggest that androgens are integral for maintaining sexual function and play a critical role in maintaining sexual health in men and women.

Dehydroepiandrosterone intra vaginal administration for the management of postmenopausal vulvovaginal atrophy

The effects of intravaginal administration of dehydroepiandrosterone (DHEA) for the management of symptomatic vulvovaginal atrophy are reviewed. A literature search related to vulvovaginal atrophy, vaginal atrophy, atrophic vaginitis, estrogen, dehydroepiandrosterone, vulvar itching, burning, dryness, dyspareunia, and libido was performed. Relevant articles addressing the incidence, management, and outcome of DHEA therapy were identified and used for this Expert Opinion. DHEA compared to a placebo is an effective treatment improving symptoms of vaginal atrophy: dyspareunia, burning, itching, and dryness. Objective parameters of vaginal atrophy, specifically pH, vaginal maturation index (VMI), and investigator-evaluated changes in the vagina: moisture, epithelia integrity and color were improved compared to baseline and placebo. There were significant improvements in libido and dyspareunia with the intravaginal use of DHEA that contribute to improved quality of life for postmenopausal women. Dehydroepiandrosterone administered intravaginally on a daily basis is an effective treatment for symptoms, and signs of vulvovaginal atrophy along with libido in postmenopausal women. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Animal models for the effective development of atrophic vaginitis therapies: possibilities and limitations

INTRODUCTION

Vaginal atrophy (VA) is an inflammation of the vagina that develops when there is a significant decrease in levels of the estrogen. Prolonged periods of hypoestrogenism may induce severe VA and treatment is essential. This is a significant problem which requires more focused attention for the development of existing and future therapies.

AREAS COVERED

This review evaluates the suitable animal models of VA, including: mice, rodents and non-human primates. It focuses particularly on the possibilities and limitations of these in vivo models for the effective development of VA therapies.

EXPERT OPINION

Hormone replacement therapy (HRT) has been prescribed and successfully used for VA. However, some studies have shown that HRT may be linked to an increased risk of breast cancer, coronary heart diseases and others risks. Thus, there is a growing interest in effective and safe alternatives to VA symptoms. There are, however, a number of things that must be considered for future drug discovery efforts. One major consideration is what animal model should be used and whether the model is appropriate for the study aim. Similarly, research studies must also consider the influencing factors on these animal models, so that these models can effectively mimic the actual disease. The authors also highlight the need to standardize research parameters to produce more reliable and reproducible data.

Proliferative and nonproliferative lesions of the rat and mouse mammary, Zymbal's, preputial, and clitoral glands

The mammary gland of laboratory rodents is an important organ for the evaluation of effects of xenobiotics, especially those that perturb hormonal homeostasis or are potentially carcinogenic. Mammary gland cancer is a leading cause of human mortality and morbidity worldwide and is a subject of major research efforts utilizing rodent models. Zymbal's, preputial, and clitoral glands are standard tissues that are evaluated in animal models that enable human risk assessment of xenobiotics. A widely accepted and utilized international harmonization of nomenclature for mammary, Zymbal's, preputial, and clitoral gland lesions in laboratory animals will improve diagnostic alignment among regulatory and scientific research organizations and enrich international exchanges of information among toxicologists and pathologists.

Effects of intravaginal dehydroepiandrosterone on vaginal histomorphology, sex steroid receptor expression and cell proliferation in the rat

OBJECTIVE

Recent clinical studies have shown that postmenopausal hormone therapy with estrogen plus progestogen increases breast cancer risk. Moreover, intravaginal estrogen-containing pills, creams and rings lead to significant systemic exposure to estrogen, thus indicating the need for a completely novel approach to alleviate vaginal atrophy in postmenopausal women.

DESIGN

We have studied the effect of intravaginal application of dehydroepiandrosterone at daily doses of 0.33 mg, 0.66 mg or 1mg in ovariectomized animals for 2 weeks, with the objective of inducing local beneficial effects in the vagina without significant systemic action.

RESULTS

After 2 weeks, serum dehydroepiandrosterone, androst-5-ene-3beta,17beta-diol and dehydroepiandrosterone-sulfate were increased over a 4h time period, but serum testosterone, estradiol, estrone and dihydrotestosterone remained below detectable levels. The suppository vehicle alone produced minimal epithelial thickening limited to the vaginal distal half. The morphological effects of dehydroepiandrosterone on vaginal mucosa were observed at the lowest dose and consisted mainly of a typical androgenic effect of epithelial mucification. No change in morphological features related to cell proliferation was observed at any dehydroepiandrosterone dose on uterus, mammary gland and skin. At the highest dose, body weight showed a significant decrease, thus indicating a systemic effect on lipid accumulation. Immunohistochemistry for androgen, estrogen alpha and progesterone receptors did not reveal any significant systemic effects in the uterus, mammary gland and skin except some suggestion of increased androgen receptor labeling in mammary gland and skin at the highest dehydroepiandrosterone dose.

CONCLUSION

The present data show that intravaginal dehydroepiandrosterone can exert beneficial effects limited to the vagina.

Long-term DHEA replacement in primary adrenal insufficiency: a randomized, controlled trial

CONTEXT

Dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS) are the major circulating adrenal steroids and substrates for peripheral sex hormone biosynthesis. In Addison's disease, glucocorticoid and mineralocorticoid deficiencies require lifelong replacement, but the associated near-total failure of DHEA synthesis is not typically corrected.

OBJECTIVE AND DESIGN

In a double-blind trial, we randomized 106 subjects (44 males, 62 females) with Addison's disease to receive either 50 mg daily of micronized DHEA or placebo orally for 12 months to evaluate its longer-term effects on bone mineral density, body composition, and cognitive function together with well-being and fatigue.

RESULTS

Circulating DHEAS and androstenedione rose significantly in both sexes, with testosterone increasing to low normal levels only in females. DHEA reversed ongoing loss of bone mineral density at the femoral neck (P < 0.05) but not at other sites; DHEA enhanced total body (P = 0.02) and truncal (P = 0.017) lean mass significantly with no change in fat mass. At baseline, subscales of psychological well-being in questionnaires (Short Form-36, General Health Questionnaire-30), were significantly worse in Addison's patients vs. control populations (P < 0.001), and one subscale of SF-36 improved significantly (P = 0.004) after DHEA treatment. There was no significant benefit of DHEA treatment on fatigue or cognitive or sexual function. Supraphysiological DHEAS levels were achieved in some older females who experienced mild androgenic side effects.

CONCLUSION

Although further long-term studies of DHEA therapy, with dosage adjustment, are desirable, our results support some beneficial effects of prolonged DHEA treatment in Addison's disease.

Physiology of female sexual function: animal models

INTRODUCTION

Data concerning the physiology of desire, arousal, and orgasm in women are limited because of ethical constraints. Aim. To gain knowledge of physiology of female sexual function through animal models.

METHODS

To provide state-of-the-art knowledge concerning female sexual function in animal models, representing the opinions of seven experts from five countries developed in a consensus process over a 2-year period.

MAIN OUTCOME MEASURE

Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.

RESULTS

Sexual desire may be considered as the presence of desire for, and fantasy about, sexual activity. Desire in animals can be inferred from certain appetitive behaviors that occur during copulation and from certain unconditioned copulatory measures. Proceptive behaviors are dependent in part on estrogen, progesterone, and drugs that bind to D1 dopamine receptors, adrenergic receptors, oxytocin receptors, opioid receptors, or gamma-amino butyric acid receptors. Peripheral arousal states are dependent on regulation of genital smooth muscle tone. Multiple neurotransmitters/mediators are involved including adrenergic, and nonadrenergic, noncholinergic agents such as vasoactive intestinal polypeptide, nitric oxide, neuropeptide Y, calcitonin gene-related peptide, and substance P. Sex steroid hormones, estrogens and androgens, are critical for structure and function of genital tissues including modulation of genital blood flow, lubrication, neurotransmitter function, smooth muscle contractility, mucification, and sex steroid receptor expression in genital tissues. Orgasm may be investigated by urethrogenital (UG) reflex, in which genital stimulation results in rhythmic contractions of striated perineal muscles and contractions of vagina, anus, and uterine smooth muscle. The UG reflex is generated by a multisegmental spinal pattern generator involving the coordination of sympathetic, parasympathetic, and somatic efferents innervating the genital organs. Serotonin and dopamine may modulate UG reflex activity.

CONCLUSIONS

More research is needed in animal models in the physiology of female sexual function.

Progress in Female Sexual Dysfunction

INTRODUCTION

Female sexual dysfunction (FSD) is a significant age-related, progressive and highly prevalent problem that affects a substantial number of women that causes personal distress and has negative effects on quality of life and interpersonal relationships.

DEFINITIONS

The female sexual response cycle consists of three phases: desire, arousal, and orgasm, and is initiated by non-adrenergic/non-cholinergic, e.g. vasoactive intestinal polypeptide and nitric oxide, neurotransmitters that maintain vascular and non-vascular smooth muscle relaxation resulting in increased pelvic blood flow, vaginal lubrication, and clitoral and labial engorgement. Furthermore, hormonal status may influence female sexual function. For the diagnosis of FSD, a detailed history should be taken initially, followed by a physical examination and laboratory studies.

CONCLUSION

Due to the fact that there has been little research and attention on FSD, our knowledge in this field is quite limited and there is still no approved therapy. Future advances in evaluation and treatment of female sexual problems are forthcoming.

Effects of dehydroepiandrosterone, Premarin and Acolbifene on histomorphology and sex steroid receptors in the rat vagina

To assess the specific estrogenic and/or androgenic effects of a potential novel hormone replacement therapy, we have examined the morphology of the rat vagina 9 months after ovariectomy (OVX) and treatment of OVX animals with dehydroepiandrosterone (DHEA), conjugated estrogens Premarin and the selective estrogen receptor modulator Acolbifene. OVX led to atrophy and inflammatory changes while Acolbifene reduced the inflammation incidence and induced mucification of the vaginal epithelium. Premarin induced a typical keratinized stratified squamous epithelium while DHEA induced stimulation of the vaginal epithelium, with mucous cells typical of an androgenic effect, combined with increased collagen fiber compactness of the lamina propria. On the other hand, after OVX, the vaginal muscle layer decreased by 46%, an effect which was 41 and 100% reversed by DHEA and Premarin, respectively. The present data show particularly interesting effects of DHEA on the three layers of the vaginal wall, namely a highly mucified epithelium, an increased muscularis thickness and increased collagen fiber compactness in the lamina propria. DHEA exerts both androgenic and estrogenic effects on the vaginal mucosa, thus providing a more physiological replacement therapy.

C19‐5‐ene Steroids in Nature

Dehydroepiandrosterone (DHEA), produced from cholesterol in the adrenals, is the most abundant steroid in our circulation. It is present almost entirely as the sulfate ester, but the free steroid is the form that serves as a precursor of estrogens and androgens, as well as 7- and 16-oxygenated derivatives. Mammalian tissues reduce the 17-keto Group of DHEA to produce androstenediol-a weak estrogen and full-fledged androgen. Its androgen activity is not inhibited by the anti-androgens commonly used to treat prostate cancer. It is probably responsible for the growth of therapy-resistant prostate cancer. DHEA is hydroxylated at the 7 alpha position, and this derivative is oxidized by 11 beta-hydroxysteroid dehydrogenase to form 7-keto DHEA. The latter is reduced by the same dehydrogenase to form 7 beta-hydroxy DHEA. When fed to rats, each of the latter three steroids induce the formation of two thermogenic enzymes in the liver. The late-term human fetus produces relatively large amounts of 16 alphahydroxy DHEA, which serves the mother as a precursor of estriol.

Sex steroid hormones differentially regulate nitric oxide synthase and arginase activities in the proximal and distal rabbit vagina

Nitric oxide synthase (NOS) and arginase have been shown to regulate nitric oxide (NO) production reciprocally in genital tissues. In animal models, NO is an important regulator of vaginal blood flow and vaginal wall contractility. In this study, we investigated the modulation of NOS and arginase activities by estrogens and androgens in the proximal and distal rabbit vagina. In intact control animals, total NOS activity was higher in the proximal (528+/-78 pmol/mg protein) than the distal (391+/-44 pmol/mg protein) vagina. However, arginase activity was higher in the distal (206+/-8 nmol/mg protein) than the proximal (64+/-5 nmol/mg protein) vagina. Ovariectomy enhanced NOS activity in the proximal but not distal vagina with concomitant decrease in arginase activity in both the proximal and distal vagina. In ovariectomized rabbits, replacement with 5alpha-dihydrotestosterone (DHT) or Delta5-androstenediol (Adiol) increased NOS activity beyond that observed in ovariectomized rabbits receiving vehicle. In contrast, DHT and Adiol treatment reduced arginase activity more than that of the ovariectomized rabbits receiving vehicle. Testosterone exhibited inconsistent effects on NOS and arginase activity in the distal and proximal vagina. Estradiol replacement in ovariectomized animals reduced NOS activity in the proximal vagina down to levels that were comparable to intact control animals. However, estradiol positively modulated arginase activity in the distal vagina. Western blot analyses indicated that in the proximal vagina, neural NOS protein levels paralleled the changes observed in enzyme activity. These observations suggest that steroid hormones differentially regulate NOS and arginase activities of the proximal and distal regions of the vagina. Although estrogen treatment reduced total NOS activity in proximal vagina, estrogens are known to enhance vaginal blood flow. This paradoxical observation may be explained by differential regulation of n-NOS and e-NOS in the proximal and distal vagina. We suggest that changes in vaginal blood flow and compliance may depend on the endocrine status and the levels of circulating androgens and estrogens.

Effects of ovariectomy and estrogen and androgen treatment on sildenafil-mediated changes in female genital blood flow and vaginal lubrication in the animal model

OBJECTIVE

Our purpose was to investigate the effects of ovariectomy and estradiol and testosterone treatment on sildenafil- induced changes in genital hemodynamics and vaginal lubrication.

STUDY DESIGN

Female New Zealand White rabbits were either kept intact or underwent ovariectomy. Two weeks after ovariectomy, animals were treated with vehicle, testosterone, or a combination of estradiol and testosterone for 14 days. Genital hemodynamics and vaginal lubrication were recorded at the end of the treatment period.

RESULTS

Ovariectomy caused a marked decrease in vaginal lubrication but did not significantly alter genital hemodynamics. In contrast to testosterone treatment of ovariectomized animals, estradiol treatment significantly increased genital blood flow and vaginal lubrication above that observed in control animals. Sildenafil administration caused a significant increase in genital hemodynamics irrespective of the hormonal status.

CONCLUSION

This study suggests that estradiol but not testosterone modulates genital hemodynamics and that sildenafil enhances genital blood flow irrespective of hormonal status.

Role of androgens in female genital sexual arousal: receptor expression, structure, and function

OBJECTIVE

In women, androgens modulate the physiological function of many reproductive and sexual organs, including the ovaries, uterus, vagina, oviducts, clitoris, and mammary gland. In this article, we review the mechanisms of androgen action and discuss new data on the effects of androgens in vaginal and clitoral tissues.

MAIN OUTCOME MEASURE(S)

In this study, we characterized the androgen receptor expression in rabbit vaginal tissues from control and ovariectomized animals treated with or without androgen replacement therapy. We investigated the effects of androgen deprivation and replacement on the expression and activity of nitric oxide synthase and arginase and on vaginal smooth muscle contractility.

RESULT(S)

Androgens enhanced nitric oxide synthase activity and down-regulated arginase activity in proximal vagina. Estrogens down-regulated nitric oxide synthase activity and increased arginase activity in distal vagina. Androgens facilitated vaginal smooth muscle relaxation to electric field stimulation and vasoactive intestinal polypeptide, whereas estrogens attenuated vaginal tissue relaxation to electric field stimulation and to vasoactive intestinal polypeptide.

CONCLUSION(S)

These observations suggest that androgens may play an important role in modulating the physiology of vaginal tissue and contribute to female genital sexual arousal.

Endocrine-disrupting chemicals: prepubertal exposures and effects on sexual maturation and thyroid activity in the female rat. A focus on the EDSTAC recommendations

In 1996, the US Environmental Protection Agency was given a mandate by Congress to develop a screening program that would evaluate whether variously identified compounds could affect human health by mimicking or interfering with normal endocrine regulatory functions. Toward this end, the Agency chartered the Endocrine Disruptor Screening and Testing Advisory Committee in October of that year that would serve to recommend a series of in vitro and in vivo protocols designed to provide a comprehensive assessment of a chemical's potential endocrine-disrupting activity. A number of these protocols have undergone subsequent modification by EPA, and this review focuses specifically on the revised in vivo screening procedure recommended under the title Research Protocol for Assessment of Pubertal Development and Thyroid Function in Juvenile Female Rats. Background literature has been provided that summarizes what is currently known about pubertal development in the female rat and the influence of various forms of pharmaceutical and toxicological insult on this process and on thyroid activity. Finally, a section is included that discusses technical issues that should be considered if the specified pubertal endpoints are to be measured and successfully evaluated.

Effects of oral administration of tamoxifen, toremifene, dehydroepiandrosterone, and vorozole on uterine histomorphology in the rat

Tamoxifen, toremifene, DHEA, and vorozole inhibit tumor growth in rodent mammary carcinoma models and are promising chemotherapeutic agents for use against breast cancer development. In the present study, the effect of these agents on uterine histomorphology following oral administration to mature ovary-intact rats (n = 380) was examined. Animals received diet only (control), tamoxifen (0.4 and 1 mg/kg of diet; 10 mg/kg BW by daily gavage), toremifene (3-30 mg/kg of diet), DHEA (24-2000 mg/kg of diet), or vorozole (0.08-1.25 mg/kg BW by daily gavage) for 28 days and were either sacrificed or returned to a basal diet and then sacrificed 21 days later. Treatment with toremifene (all doses) or tamoxifen (1 and 10 mg/kg) for 28 days produced a decrease (P<0.05) in overall uterine size and myometrial thickness; however, uterine luminal and glandular epithelia cell height increased (P<0.05) compared with control. These compartmentalized uterotrophic and antiestrogenic effects of toremifene and tamoxifen were still apparent after 21 days post-treatment. Administration of DHEA (2000 mg/kg of diet) for 28 days had dramatic uterotrophic effects, increasing (P<0.05) overall uterine size and stimulating all three uterine compartments (epithelia, stroma, and myometrium). The other doses of DHEA, however, were not uterotrophic. Interestingly, after removal of DHEA from the diet, uterine weight and myometrial thickness decreased (P<0.05). Vorozole (1.25 mg/kg) administration for 28 days had differential, compartmentalized uterine effects, producing an increase (P<0.05) in epithelial cell height, a decrease (P<0.05) in stromal size, but no change in myometrial thickness. After 21 days postadministration of vorozole, luminal epithelial cell height was increased (P<0.05) compared with control. The data suggest that oral administration of tamoxifen, toremifene, DHEA, and vorozole results in differential, compartmentalized effects in the uterus that are highly dependent on treatment dose. The data may have implications for risk assessment of these agents prior to administration to healthy, cancer-free women.