From an earlier post,
DHT has an estrogenic action,
The existence of this estrogenic DHT metabolite has raised the possibility that estradiol may not be the major estrogen in males [29]. For instance, in the prostate there is a growing body of evidence that 3β-diol, acting through ERβ, may regulate important physiological events.
Recent data have shown that DHT may be converted into 5α-androstane- 3β-17β-diol (3β-diol) in a virtually irreversible reaction. Once considered inactive, 3β-diol is present in high concentrations in the male and indeed has biological activity. However, 3β-diol does not bind to the androgen receptor (AR), but rather to ERα and ERβ, with higher affinity for ERβ. Based upon these findings, we hypothesized that the modulation of AQP9 by DHT could be indirectly mediated by 3β-diol.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1615873/
Effects of 3-beta-diol, an androgen metabolite with intrinsic estrogen-like effects,
Abstract
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 fluids.
a) It has been shown that 3β-diol may have hormonal activity, not acting through the AR, but rather as a ligand for both ERα and ERβ.
b) 3β-diol has higher affinity for ERβ [31], which is abundant in the efferent ductule epithelium [40].
c)
In human testis, the 3β-diol concentration is higher than DHT and estradiol [44,45]. It is reasonable to postulate that high concentrations of this metabolite may enter the lumen of efferent ductules.
d) The existence of this estrogenic DHT metabolite has raised the possibility that estradiol may not be the major estrogen in males [29]. For instance, in the prostate there is a growing body of evidence that 3β-diol, acting through ERβ, may regulate important physiological events [26,28,32,46].
Also noteworthy is the fact that 3β-diol stimulates ERβ induced transcriptional activity equal to the cognate ligand estradiol, and the transcriptional selectivity of 3β-diol for ERβ is much greater than its binding selectivity [30,46]
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Concentrations of aromatase and estradiol in the prostate are low, indicating that estradiol may not be the only estrogenic molecule to play a role in the prostate. It is known that DHT can be metabolized to 5alpha-androstane-3beta,17beta-diol (3beta-diol), a hormone that binds to ERbeta but not to AR. The concentration of 3beta-diol in prostate is much higher than that of estradiol. Based on the high concentration of 3beta-diol and since this metabolite is a physiological ERbeta ligand, we hypothesized that 3beta-diol would be involved in the regulation of ERbeta expression.
An endocrine pathway in the prostate, ERbeta, AR, 5alpha-androstane-3beta,17beta-diol, and CYP7B1, regulates prostate growth.
http://www.ncbi.nlm.nih.gov/pubmed/12370428