Estrogen in the male. My laboratory conducts research in the areas of male
reproductive biology, endocrinology and toxicology,
with the following specific interests: spermatogenesis, testicular
growth and development, structure and function of the epididymis
and the role of estrogens in male reproduction. A major discovery
was published in Nature
(1997) 390, 509-512, showing for the first time an important
function for estrogen in the male reproductive tract. Estrogen
is considered the "female" hormone, whereas testosterone
is considered the "male" hormone. Both hormones, however,
are present in both sexes. Thus, sexual distinctions are not
qualitative differences, but rather due to quantitative divergence
in hormone concentrations and differential expressions of steroid
hormone receptors. In males, oestrogen is present in low concentrations
in blood, but can be extraordinarily high in semen and as high
as 250 pg/ml in rete testis fluids, which is higher than serum
estradiol in the female. It is well known that male reproductive
tissues express oestrogen receptors; yet, the role of oestrogen
in male reproduction had remained an open question until now.
In this paper, we were able to show that estrogen regulates reabsorption
of luminal fluid in the head of the epididymis. This was the
first demonstration of a physiological function for oestrogen
in male reproductive organs. Disruption of this essential function
causes sperm to enter the epididymis diluted, rather than concentrated,
resulting in infertility.
Molecular mechanism of estrogen function
in the male. We have now determined
that estrogen regulates expression of the Na+/H+ exchanger-3
(NHE3) and the rate of (22)Na+ transport, sensitive to a NHE3
inhibitor. Immunohistochemical staining for NHE3, carbonic anhydrase
II (CAII) and aquaporin-I (AQP1) was decreased in ERa knockout (aERKO) efferent
ductules. Targeted gene deficient mice were compared to aERKO and the
NHE3 knockout and CAII deficient mice showed aERKO-like fluid accumulation,
but only the NHE3 knockout and aERKO mice were infertile. Northern blot analysis showed
decreases in mRNA for NHE3 in aERKO and antiestrogen-treated mice. The changes in
AQP1 and CAII in aERKO appeared to be secondary, due to the disruption
of apical cytoarchitecture. Ductal epithelial ultrastructure
was abnormal only in aERKO mice. Thus, in the male, estrogen regulates one
of the most important epithelial ion transporters and maintains
epithelial morphological differentiation in efferent ductules
of the male, independent of its regulation of Na+ transport.
Finally, these data raise the possibility of targeting ERa in developing
a contraceptive for the male. Proc.
Natl. Acad. Sci. USA (2001) 98:
An understanding of estrogen's function in the male reproductive
tract is limited and estrogen receptor (ER) localization in the
reproductive tract of the adult male rat has not been described.
In the Nov/Dec issue of J.
of Andrology, we present data showing the location of
ERalpha by immunohistochemistry using ER21 antibody, which recognizes
only ERalpha. Strongest immunoreactivity was seen in epithelia
of ductuli efferentes and of the initial segment of the epididymis.
Nuclei of both ciliated and nonciliated cells were positive.
The epithelium of the rete testis, caput, corpus and cauda epididymides
stained less intensely for ERalpha. The vas deferens epithelium
was ERalpha negative. Stromal tissue in the excurrent ducts was
also ERalpha positive. Using 3H-estradiol autoradiography, specific
binding of estradiol was seen in nuclei of ductuli efferentes.
ERalpha mRNA expression was greatly enhanced in ductuli efferentes
compared to other regions of the male tract and was 3.5 times
greater than in uterus. For comparison, the presence of ERß
was determined using reverse transcription-polymerase chain reaction
(RT-PCR) amplification. ERßmRNA was expressed throughout
the male tract and in prostate. These results indicate that all
organs in the male excurrent ductal system of the rat express
ERa and are potential targets of estrogen. However, the ductuli
efferentes are the site of most intense ERa expression. The role
of ERß remains to be determined, but its expression appears
ubiguitous in the male tract. References
Stem cell biology
Our stem cell research came about through a discovery at Washington University School of Medicine in St. Louis. Dr. Ken Murphy at Wash U discovered that knocking out a transcription factor, Etv5 (from the PEA-3 family), led to male infertility and through collaboration we were able to demonstrate that this factor was specific for the Sertoli and spermatogonial stem cells during the first wave of spermatogenesis and is responsible for stem cell self renewal. This study was first published in Nature 436:1030 and subsequent studies have been in collaboration with Dr. Marie-Claude Hofmann and Dr. Paul S. Cooke. Through both basic and applied research, we seek a better understanding of structure and function of the male reproductive tract and improvements in reproductive and endocrine health.
Testicular and efferent ductule effects of carbendazim (methyl
2-benzimidazole carbamate), a metabolite of the fungicide benomyl,
were determined in the adult rat after a single exposure. Effects
were first seen beginning at 8 h post-exposure as an increase
in testis weight; then decreases in testicular spermatid numbers,
epididymal sperm reserves, and in the percentage of morphologically
normal cauda sperm. Significant testicular and efferent ductal
alterations occurred in animals treated with dosages of 100 mg/kg
or greater. A dose-dependent increase in testicular weight at
2 days post-treatment was accompanied by increases in seminiferous
tubular diameter, and excessive loss of immature germ cells in
a stage-dependent manner. There was also a dose dependent increased
incidence of occlusions in the efferent ductules. The occluded
ductules were characterized by severe inflammation and epithelium
disorganization. At 70 days post treatment, there were dose-dependent
decreases in mean testis weight and mean seminiferous tubular
diameter. Only minimal long-term effects were seen at 50 mg/kg.
In testes exhibiting greater than 25% seminiferous tubular atrophy
(100 mg/kg or greater dosages), 100% of the testes were associated
with efferent ductules containing occlusions and the caput sperm
numbers were significantly reduced. Occlusions, abnormal ductules,
fibrosis, spermatic granulomas and mineralizations were observed
in the ductuli efferentes. Long-term effects of carbendazim on
the testis were induced primarily by the ductal occlusions. Carbendazim
effects on the male reproductive system were found to be more
severe than those produced by the fungicide benomyl.