Abstract
Testosterone and estrogen are no longer considered male only and female only hormones. Both hormones are important in both sexes. It was known as early as the 1930's that developmental exposure to a high dose of estrogen causes malformation of the male reproductive tract, but the early formative years of reproductive biology as a discipline did not recognize the importance of estrogen in regulating the normal function of the adult male reproductive tract. In the adult testis, estrogen is synthesized by Leydig cells and the germ cells, producing a relatively high concentration in rete testis fluid. Estrogen receptors are present in the testis, efferent ductules and epididymis of most species. However, estrogen receptor-α is reported absent in the testis of a few species, including man. Estrogen receptors are abundant in the efferent ductule epithelium, where their primary function is to regulate the expression of proteins involved in fluid reabsorption. Disruption of the α-receptor, either in the knockout (αERKO) or by treatment with a pure antiestrogen, results in dilution of cauda epididymal sperm, disruption of sperm morphology, inhibition of sodium transport and subsequent water reabsorption, increased secretion of Cl-, and eventual decreased fertility. In addition to this primary regulation of luminal fluid and ion transport, estrogen is also responsible for maintaining a differentiated epithelial morphology. Thus, we conclude that estrogen or its α-receptor is an absolute necessity for fertility in the male.
Highlights
It was known as early as the 1930's that the developing testis was responsive to the "female" hormone [[1], reviewed by [2]]
During the formative years of reproductive biology as a discipline it was suggested that estrogen might be important in the male; even in the early 1990's many scientists considered estrogen receptor presence in the adult male reproductive tract to be a remnant from the indifferent sex stage of embryological differentiation [7]
In 1993, in collaboration with the laboratories of Bahr and Bunick [49], we reported for the first time that P450arom is present in testicular germ cells of the adult male mouse
Summary
It was known as early as the 1930's that the developing testis was responsive to the "female" hormone [[1], reviewed by [2]]. In the decade of the 90's new discoveries in the male led to the hypothesis that estrogen has important functions in the adult male reproductive tract, but that estrogen and its α-receptor are "essential" for normal fertility This new paradigm for estrogen's role in the male began with the discovery that testicular germ cells and epididymal sperm contain aromatase and synthesize estrogen [49]. This discovery explained the presence of a high concentration of estradiol in rete testis of the rat [41] and provided a source of estrogen for the high concentration of receptors that were subsequently found to populate the head of the male reproductive tract [50,51,52,53,54,55]. It would be interesting to determine if aromatase is expressed in the
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