Effects of 3-beta-diol, an androgen metabolite with intrinsic estrogen-like effects, in modulating the aquaporin-9 expression in the rat efferent ductules

BACKGROUND: Fluid homeostasis is critical for normal function of the male reproductive tract and aquaporins (AQP) play an important role in maintenance of this water and ion balance. Several AQPs have been identified in the male, but their regulation is not fully comprehended. Hormonal regulation of AQPs appears to be dependent on the steroid in the reproductive tract region. AQP9 displays unique hormonal regulation in the efferent ductules and epididymis, as it is regulated by both estrogen and dihydrotestosterone (DHT) in the efferent ductules, but only by DHT in the initial segment epididymis. Recent data have shown that a metabolite of DHT, 5-alpha-androstane-3-beta-17-beta-diol (3-beta-diol), once considered inactive, is also present in high concentrations in the male and indeed has biological activity. 3-beta-diol does not bind to the androgen receptor, but rather to estrogen receptors ER-alpha and ER-beta, with higher affinity for ER-beta. The existence of this estrogenic DHT metabolite has raised the possibility that estradiol may not be the only estrogen to play a major role in the male reproductive system. Considering that both ER-alpha and ER-beta are highly expressed in efferent ductules, we hypothesized that the DHT regulation of AQP9 could be due to the 3-beta-diol metabolite. METHODS: To test this hypothesis, adult male rats were submitted to surgical castration followed by estradiol, DHT or 3-beta-diol replacement. Changes in AQP9 expression in the efferent ductules were investigated by using immunohistochemistry and Western blotting assay. RESULTS: Data show that, after castration, AQP9 expression was significantly reduced in the efferent ductules. 3-beta-diol injections restored AQP9 expression, similar to DHT and estradiol. The results were confirmed by Western blotting assay. CONCLUSION: This is the first evidence that 3-beta-diol has biological activity in the male reproductive tract and that this androgen metabolite has estrogen-like activity in the efferent ductules, whose major function is the reabsorption of luminal fluid

The antiestrogen ICI 182,780 decreases the expression of estrogen receptor-alpha but has no effect on estrogen receptor-beta and androgen receptor in rat efferent ductules

BACKGROUND: The antiestrogen ICI 182,780 has been used successfully as an alternative experimental model for the study of estrogen action in the rodent adult male reproductive tract. Although ICI 182,780 causes severe alterations in testicular and efferent ductule morphology and function, the effects on the expression of estrogen and androgen receptors in the male have not been shown. METHODS: In the present study, adult male rats were treated with ICI 182,780 for 7 to 150 days, to evaluate the time-response effects of the treatment on the pattern of ERα, ERβ and AR protein expression in the efferent ductules. The receptors were localized using immunohistochemistry. RESULTS: ERα, ERβ and AR have distinct cellular distribution in the testis and efferent ductules. Staining for ERα is nearly opposite of that for ERβ, as ERα shows an increase in staining intensity from proximal to distal efferent ductules, whereas ERβ shows the reverse. Androgen receptor follows that of ERα. ICI 182,780 caused a gradual but dramatic decrease in ERα expression in the testis and efferent ductules, but no change in ERβ and AR expression. CONCLUSIONS: The differential response of ERα and ERβ proteins to ICI 182,780 indicates that these receptors are regulated by different mechanisms in the male reproductive tract

Enfrentando desafios da formação docente na pós-graduação: descrição de uma experiência

This manuscript presents description and analysis of the pedagogical practice, illustrating the challenges of preparing teacher for higher education. The text dialogues with elements concerning teacher training and the guidelines of legislation related to these themes, as a way to contextualize the discussion. Specifically, this description shares with the reader the entire process of design, development, implementation and evaluation of the discipline Supervised Teaching Practice, at a graduate program of the biological area at the Federal University of Minas Gerais, Brazil. The findings show that the pedagogical training is both necessary and possible in all graduate level courses, combining the practical activities inherent to the teaching stage in undergraduate classes, with theoretical-practical discussions and reflections on teaching. That way brings benefits for the graduate students and future teachers as well as the undergraduate students.Este artigo apresenta descrição e análise da prática pedagógica, buscando trazer contribuições ao enfren-tamento do desafio da formação docente para o ensino superior. O texto dialoga com elementos acerca da formação docente e com diretrizes da legislação em torno dessa temática, como forma de contextualizar a discussão. No relato da experiência, compartilha-se com o leitor todo o processo de concepção, desen-volvimento, aplicação e avaliação de uma disciplina de Estágio Didático de um programa de pós-graduação da área biológica na Universidade Federal de Minas Gerais. As conclusões demonstram que é necessário e possível a formação pedagógica em cursos de mestrado e doutorado, aliando as atividades práticas ine-rentes ao estágio docente em turmas de graduação, com discussões e reflexões teórico-práticas sobre a docência. Esse formato traz benefícios tanto para os alunos da pós-graduação, futuros docentes, quanto para os alunos da graduação.   &nbsp

Differential hormonal regulation of estrogen receptors ERalpha and ERbeta and androgen receptor expression in rat efferent ductules

Estrogen receptors, in addition to the androgen receptor (AR), are expressed at high levels in efferent ductules of the male reproductive tract and it is now well recognized that estrogen receptor (ER) α is required for the maintenance of normal structure and function of the ductules. However, little is known regarding the hormonal regulation of the receptors themselves in the male. In the present study, efferent ductule ligation and castration, followed by replacement with testosterone, dihydrotestosterone (DHT) or estradiol was used to investigate the relative importance of circulating and luminal sources of steroid for the modulation of ERα, ERβ and AR in rat efferent ductules. Uni- or bilateral castration and ligation did not affect the expression of ERα and ERβ, but bilateral castration caused down-regulation of AR. Replacement with DHT and testosterone alone or in combination with estradiol caused the recovery of AR expression to control levels. A slight recovery of AR was also observed after estrogen replacement. ERα expression was decreased to nearly undetectable levels after estrogen replacement. On the other hand, ERβ did not show evident effects following any of the treatments, suggesting a constitutive expression of this receptor. This differential modulation of the steroid hormone receptors highlights the importance of maintaining a physiological androgen-estrogen balance to regulate the structure and function of efferent ductules in the male

Oviduct morphology and estrogen receptors ERα and ERβ expression in captive Chinchilla lanigera (Hystricomorpha: Chinchillidae)

Chinchilla lanigera is a hystricomorph rodent from South America whose reproductive biology presents particular characteristics that distinguishes it from other Rodentia species, such as low reproductive rate, seasonal breeding pattern, and long estrous cycle. Nevertheless, reproductive features in female chinchillas are still poorly investigated, with a scarce knowledge concerning the estrous cycle and the histology of reproductive organs. In this study, we investigate the morphology, histomorphometry, secretory activity, and immunolocalization of estrogen receptors ERα and ERβ in oviducts of nulliparous chinchillas, euthanized at fall season in Brazil. Follicular phase of estrous cycle of all studied animals was characterized by ovary and uterine morphology inspection, as well as vaginal cytology. Similar to other mammals, the oviduct wall of infundibulum, ampulla and isthmus was composed of mucosa, muscle, and serosa layers. Morphometric data of oviduct layers were used for identifying each oviduct segment. In the follicular phase, the oviduct was characterized by intense secretory activity, mainly in the ampulla, and expression of ERα and ERβ throughout the oviduct epithelium. Both ERα and ERβ were also detected in the connective tissue and smooth muscle cells. Our findings point out to the important role of estrogen in this female organ. Similar wide distribution of both ER proteins has been described for human Fallopian tube. Taken together, our data add to the understanding of the reproductive biology of female chinchillas, and may assist in the intensive breeding of this species and any eventual endeavor for conservation of chinchillas in the wild

Expression of the proto-oncogene c-fos and the immunolocalization of c-fos, phosphorylated c-fos and estrogen receptor beta in the human testis

Spermatogenesis is under the control of a complex endocrine and paracrine system, including estrogen receptor (ER) signaling. In many target cells, ER promotes the transcription of c-fos and other protooncogenes to regulate cell growth and differentiation. Thus, in this study we evaluated the expression of the proto-oncogene c-fos and the immunolocalization of cfos, phosphorylated c-fos and ERbeta proteins in the human testis. Testis tissue samples were obtained from 12 men undergoing orchiectomy as adjuvant treatment for prostate cancer, and were stained by immunohistochemistry for c-fos, phosphorylated c-fos and ERbeta localization. Both forms of c-fos proteins were immunoreactive, mainly in germ cells (spermatogonia, spermatocytes and spermatids) and Sertoli cells, while ERbeta was primarily present in somatic cells (Leydig, Sertoli and myofibrillar cells). In addition, testicular biopsies obtained from infertile men with obstructive azoospermia/normal spermatogenesis (n=8) or non-obstructive azoospermia/severely impaired spermatogenesis (n=12) were evaluated for c-fos and ERbeta mRNA levels using real time polymerase chain reaction. The expression of c-fos mRNA was significantly lower (fold change = 0.08, p<0.05) whereas that of ERbeta mRNA was higher (fold change = 9.43, p<0.05) in the testis of men with non-obstructive azoospermia compared to those with obstructive azoospermia. These findings suggest a complex interrelation between estrogen signaling and c-fos transcriptional activity within the human testis, with the increase of ERbeta mRNA being putatively a compensatory mechanism for lower c-fos expression in infertile men with damaged spermatogenesis