Absence of Estrogen Receptor Alpha Leads to Physiological Alterations in the Mouse Epididymis and Consequent Defects in Sperm Function1

Abstract

Male mice deficient in ESR1 (ERalpha) (Esr1KO mice) are infertile, and sperm recovered from the cauda epididymis exhibit reduced motility and fail to fertilize eggs in vitro. These effects on sperm appear to result from defective epididymal function and not a direct effect on spermatogenesis, as Esr1KO germ cells transplanted into wild-type testes yield normal offspring. We hypothesized that the previously described defect in efferent duct fluid reabsorption would lead to alterations in the epididymal fluid milieu, which would negatively impact sperm function. Analysis of the epididymal fluid revealed that the Esr1KO maintains a higher luminal pH throughout the epididymis, confirming an inability of the efferent ducts and/or epididymis to properly acidify the luminal contents. Subsequent studies showed that these abnormalities were not the result of global defects in epididymal function since protein secretion by the Esr1KO epididymis appeared normal as judged by SDS-PAGE of total secreted proteins and by immunoblotting of candidate secreted proteins. To gain insight into the basis of the aberrant fluid homeostasis in the Esr1KO epididymis, the expression of several enzymes and transporters known to be involved in acid/base regulation were analyzed. The levels of SLC9A3 (NHE3) as well as carbonic anhydrase XIV and SLC4A4 (NBC1) were all reduced in the proximal portion of the Esr1KO epididymis, while other components appeared unaffected, including other ion transporters and ATP6V0A1 (V-ATPase). The altered luminal milieu of the Esr1KO epididymis was shown to lead to a corresponding increase in the intracellular pH of Esr1KO sperm, relative to sperm from control animals. Since pH and bicarbonate ions are critical regulators of sperm cAMP levels and motility, we attempted to bypass the abnormal luminal and intracellular environment by supplementing sperm with exogenous cAMP. This treatment rescued all defective motility parameters, as assayed by CASA, further showing that motility defects are not intrinsic to the sperm but, rather, result from the abnormal epididymal milieu.

The immunoexpression of androgen receptor, estrogen receptors alpha and beta, vanilloid type 1 receptor and cytochrome p450 aromatase in rats testis chronically treated with letrozole, an aromatase inhibitor

“…As a result of adult male rats treatment with letrozole, we observed changes in ERa and ERb expression in testis. We concluded, according to results of other authors [2,51,52] and ours, that the chronical treatment of male rats with aromatase inhibitor, and in consequence estrogen deficiency, can follow ERs down-regulation.…”

The Blood-Testis Barrier and Its Implications for Male Contraception

“…Estrogen is crucial to male reproductive function, including the male reproductive tract (e.g., efferent ductules, epididymis), testis, spermatogenesis, and the BTB (Li et al, 2009d;Carreau and Hess, 2010;Joseph et al, 2010aJoseph et al, ,b, 2011Cheng et al, 2011a;Hess et al, 2011). A role for estrogen as a locally acting male hormone in the testis was first demonstrated in adult mice deficient in ER␣ (Hess et al, 1997).…”

Vitamin D metabolism, sex hormones, and male reproductive function

“…Estrogen regulates fluid reabsorption in the reproductive tract and the estrogen receptor (Er) a KO male is infertile, although testes histology appears normal until puberty, when the tubules begin to degenerate. Sperm recovered from the cauda epididymis of these mice exhibit reduced motility and failed to fertilize eggs in vitro (Hess et al 1997, Carreau & Hess 2010, Joseph et al 2010. Moreover, male mice with deficient aromatase do not present with a severe phenotype and were initially fertile but developed progressive infertility and disrupted spermatogenesis after 4.5 months to 1 year.…”