Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: The goal of the studies was to determine whether androgens and estrogens play a role in epididymal function in the boar epididymis. The specific aims were to determine 1. estrogen and androgen receptor expression in relation to steroid concentrations in the adult boar epididymis, 2. the effects of reduced estrogen production on epididymal development and efferent duct morphology, and 3. the effects of reduced estrogen on expression of lactoferrin in the boar epididymis. In the first study epididymal (caput, corpus, cauda) and testicular samples of 5 boars were collected to identify the site of estrogen receptor alpha (ERalpha), estrogen receptor beta (ERbeta) and androgen receptor (AR). Concentrations of testosterone (T), estradiol (E2) and estrogen conjugates (EC) in the tissue were also determined. AR and ERbeta were identified in the principal and basal cells of all three epididymal regions. ERalpha was identified in the principal cells of the caput, some
cells of the corpus and was not present in the cauda. T, E2 and EC were significantly lower in the epididymis compared with the testis. The epididymal regions were not significantly different from each other for T or E2. EC were significantly higher in the corpus than either the caput or cauda. These results suggest that androgens and estrogens are important for proper epididymal function. Differences in T and E2 regulation are likely due to differences in receptor expression. In the second study 28 littermate pairs of boars were treated with Letrozole, a drug that inhibits the conversion of T to E2, or with saline from 1 week old until castration at 2 through 8 months. Efferent duct morphology was not different between control and Letrozole-treated animals at any examined age. AR, ERalpha, and ERbeta were expressed in the epithelial cells of the efferent ducts at all ages; expression was similar in control and treated animals. No difference was observed in the expression of AR,
ERalpha, and ERbeta between control and treated animals. In summary, estrogen appears to be important for development of the epididymis. Results suggest that the high levels of estrogens are not required for regulation of efferent ducts. In the third study 21 littermate pairs of boars were treated with saline or Letrozole from 1 week old until castration at 2 through 8 months. Epididymal tissue was collected at castration and processed for localization of lactoferrin. Epididymal and testicular tissues were also collected from five mature boars and processed in a similar fashion. Lactoferrin was localized in the principal cell of the caput, corpus and cauda of developing boars but only in the corpus and cauda of mature boars. Basal cells were negative for lactoferrin. Sperm in the corpus and cauda was also positive for lactoferrin. The amount of lactoferrin increased with age in the corpus and cauda regardless of treatment. Reduced endogenous estrogen in the epididymis during
development did not affect the amount of lactoferrin between control and Letrozole-treated animals. Lactoferrin expression in the epididymis of the developing boar does not appear to be regulated by estrogen. PARTICIPANTS: Two Ph.D. students, Eeman At-Taras and Chris Pearl worked on this project under the supervision of Dr. Jan Roser. A faculty member in the Department of Animal Science, UC Davis, Dr. Trish Berger, was a collaborator on this project. This project generated 3 publications and presented new information that has been incorporated into a grant written by Dr. Berger, Dr. Al Conley (UC Davis) and Dr. Roser. The grant has been submitted to the USDA for 2008-2011 funding. Dr. At-Taras is now a professor at a University in Saudia Arabia. Dr. Pearl is now a post-doc at Washington University Medical School in St. Louis. TARGET AUDIENCES: The results of this work will be of great interest to breeders in the pig industry. Previous work in our lab demonstrated that by inhibiting
estrogen production in the pre-pubertal boar, testicular size increases by 25% and with it a significant increase in sperm production (At-Taras et al., 2006, J Androl 27:552). The studies herein indicate that epididymal function is not compromised in the adult after treatment to piglets with the estrogen inhibitor. Taken together these studies suggest that breeders may be able to increase reproductive efficiency in their boars by treating piglets with an estrogen inhibitor. PROJECT MODIFICATIONS: There were no modifications or changes made to the research approach or protocols during the studies presented.
Impacts
These studies have enhanced our understanding of the role that androgens and estrogens play in the control of epididymal function. This is critical to the animal industry as sperm attain their motility and fertilizing ability in the epididymis. Small differences in fertilizing capacity may have very significant economic effects on the animal industry; the number of piglets born per year, labor efficiency and market value. Understanding of epididymal function will contribute to improve efficacy of cooled and frozen semen for artificial insemination.
Publications
- Pearl CA, Berger T, Roser JF. 2007. Estrogen and androgen receptor expression in relation to steroid concentrations in the adult boar epididymis. Domest Anim Endocrinol 33: 451-459.
- Pearl CA, At-Taras E, Berger T, Roser JF. 2007. Reduced endogenous estrogen delays epididymal development but has no effect on efferent duct morphology in boars. Reprod 134:593-604.
- Pearl CA, Roser JF. 2007. Expression of lactoferrin in the boar epididymis: Effects of reduced estrogen. Domest Anim Endocrinol Feb 5 [Epub ahead of print].
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Progress 10/01/02 to 09/30/07
Outputs
OUTPUTS: The goal of the studies was to determine whether androgens and estrogens play a role in epididymal function in the boar epididymis. The specific aims were to determine 1. estrogen and androgen receptor expression in relation to steroid concentrations in the adult boar epididymis, 2. the effects of reduced estrogen production on epididymal development and efferent duct morphology, and 3. the effects of reduced estrogen on expression of lactoferrin in the boar epididymis. In the first study epididymal (caput, corpus, cauda) and testicular samples of 5 boars were collected to identify the site of estrogen receptor alpha (ERalpha), estrogen receptor beta (ERbeta) and androgen receptor (AR). Concentrations of testosterone (T), estradiol (E2) and estrogen conjugates (EC) in the tissue were also determined. AR and ERbeta were identified in the principal and basal cells of all three epididymal regions. ERalpha was identified in the principal cells of the caput, some cells of the corpus and was not present in the cauda. T, E2 and EC were significantly lower in the epididymis compared with the testis. The epididymal regions were not significantly different from each other for T or E2. EC were significantly higher in the corpus than either the caput or cauda. These results suggest that androgens and estrogens are important for proper epididymal function. Differences in T and E2 regulation are likely due to differences in receptor expression. In the second study 28 littermate pairs of boars were treated with Letrozole, a drug that inhibits the conversion of T to E2, or with saline from 1 week old until castration at 2 through 8 months. Efferent duct morphology was not different between control and Letrozole-treated animals at any examined age. AR, ERalpha, and ERbeta were expressed in the epithelial cells of the efferent ducts at all ages; expression was similar in control and treated animals. No difference was observed in the expression of AR, ERalpha, and ERbeta between control and treated animals. In summary, estrogen appears to be important for development of the epididymis. Results suggest that the high levels of estrogens are not required for regulation of efferent ducts. In the third study 21 littermate pairs of boars were treated with saline or Letrozole from 1 week old until castration at 2 through 8 months. Epididymal tissue was collected at castration and processed for localization of lactoferrin. Epididymal and testicular tissues were also collected from five mature boars and processed in a similar fashion. Lactoferrin was localized in the principal cell of the caput, corpus and cauda of developing boars but only in the corpus and cauda of mature boars. Basal cells were negative for lactoferrin. Sperm in the corpus and cauda was also positive for lactoferrin. The amount of lactoferrin increased with age in the corpus and cauda regardless of treatment. Reduced endogenous estrogen in the epididymis during development did not affect the amount of lactoferrin between control and Letrozole-treated animals. Lactoferrin expression in the epididymis of the developing boar does not appear to be regulated by estrogen. PARTICIPANTS: Two Ph.D. students, Eeman At-Taras and Chris Pearl worked on this project under the supervision of Dr. Jan Roser. A faculty member in the Department of Animal Science, UC Davis, Dr. Trish Berger, was a collaborator on this project. This project generated 3 publications and presented new information that has been incorporated into a grant written by Dr. Berger, Dr. Al Conley (UC Davis) and Dr. Roser. The grant has been submitted to the USDA for 2008-2011 funding. Dr. At-Taras is now a professor at a University in Saudia Arabia. Dr. Pearl is now a post-doc at Washington University Medical School in St. Louis. TARGET AUDIENCES: The results of this work will be of great interest to breeders in the pig industry. Previous work in our lab demonstrated that by inhibiting estrogen production in the pre-pubertal boar, testicular size increases by 25% and with it a significant increase in sperm production (At-Taras et al., 2006, J Androl 27:552). The studies herein indicate that epididymal function is not compromised in the adult after treatment to piglets with the estrogen inhibitor. Taken together these studies suggest that breeders may be able to increase reproductive efficiency in their boars by treating piglets with an estrogen inhibitor. PROJECT MODIFICATIONS: There were no modifications or changes made to the research approach or protocols during the studies presented.
Impacts
These studies have enhanced our understanding of the role that androgens and estrogens play in the control of epididymal function. This is critical to the animal industry as sperm attain their motility and fertilizing ability in the epididymis. Small differences in fertilizing capacity may have very significant economic effects on the animal industry; the number of piglets born per year, labor efficiency and market value. Understanding of epididymal function will contribute to improve efficacy of cooled and frozen semen for artificial insemination.
Publications
- Pearl CA, At-Taras E, Berger T, Roser JF. 2007. Reduced endogenous estrogen delays epididymal development but has no effect on efferent duct morphology in boars. Reprod 134:593-604.
- Pearl CA, Roser JF. 2007. Expression of lactoferrin in the boar epididymis: Effects of reduced estrogen. Domest Anim Endocrinol Feb 5 [Epub ahead of print].
- Pearl CA, Berger T, Roser JF. 2007. Estrogen and androgen receptor expression in relation to steroid concentrations in the adult boar epididymis. Domest Anim Endocrinol 33: 451-459.
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Progress 01/01/06 to 12/31/06
Outputs
Experiments were designed to test the hypothesis that reduced endogenous estrogen in the boar would alter efferent duct and epididymal morphology and steroid receptor expression. Efferent duct morphology was not different between control and aromatase-inhibited animals at any age examined (two to eight months). Androgen receptor, estrogen receptor alpha and estrogen receptor beta were expressed in the epithelial cells of the efferent ducts at all ages although no difference was seen between control and treated animals. The lack of difference is surprising suggesting that estrogen receptors and fluid reabsorption by the efferent ducts may not be regulated by estrogen in boars. Androgen receptor, estrogen receptor alpha and estrogen receptor beta are expressed in all three epididymal regions but no difference was seen between control and treated animals. Development of the caput and corpus is delayed in animals with reduced endogenous estrogen, but this delay is
transient since the morphology is similar between control and treated animals at eight months. Interestingly, the cauda epididymis does not show a delay in development, but development is progressed at two months in treated animals. These results suggest that estrogen is important for development of the epididymis and that the cauda may be differentially regulated compared with the caput and corpus epididymis. Additional experiments were designed to test the hypothesis that lactoferrin expression in the boar epididymis is regulated by estrogen. The expression of lactoferrin was investigated in the epididymis of mature boars and in the epididymis of vehicle control and aromatase inhibited animals by immunocytochemistry. Lactoferrin was localized in the caput, corpus and cauda of developing boars but only in the corpus and cauda of mature boars. The efferent ducts and testes were negative for lactoferrin. Concentrations of estradiol increase with age in the boar and this increase could
be responsible for the stronger intensity of immunostaining observed in eight month and mature boars compared with younger animals. However, reducing endogenous estrogens during development did not affect the intensity of immunostaining between control and aromatase-inhibited animals. Therefore, lactoferrin may be estrogen regulated in the boar epididymis, but other factors, perhaps androgens, must be involved in its regulation as well.
Impacts
Increased understanding of the role that steroids play in the epididymis will contribute to a better understanding of epididymal function. This is critical to the animal industry as sperm attain ability to fertilize in the epididymis. Small differences in fertilizing ability have very significant economic effects on the animal industry. Increased understanding of epididymal function will also contribute to improve efficacy of cooled and frozen semen for artificial insemination.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
Epididymal tissue was processed from adult boars (1-2.5 years) and from control and letrozole treated animals (2-8 months) to investigate the potential steroid regulation of the boar epididymis. In adult boars, the concentration of testosterone and estradiol were significantly higher in the testis compared with the epididymis (p < 0.001) but the epididymal regions were not significantly different from one another (p > 0.4). The lack of difference among the epididymal regions is surprising; however, this implies that estradiol and testosterone are equally available in the tissue to regulate all three epididymal regions. Assays to determine steroid concentrations in control and letrozole-treated epididymides are currently in progress. Androgen receptor (AR) and estrogen receptor beta were localized in the principal cells of the caput, corpus and cauda at all ages. AR immunostaining was strongest at 2 months of age compared to 8 months of age. Estrogen receptor alpha was
localized in the principal cells of the caput, corpus and cauda prior to puberty. By 8 months of age ER-alpha immunostaining in the corpus and cauda was reduced, similar to the pattern seen in adult boars. No major differences were seen in immunostaining for AR, ER-alpha and ER-beta between control and treated epididymides. Results of Taqman RT-PCR for mRNA of the receptors in 2 and 8 month animals confirm the immunostaining results. Together these results suggest that epididymal development and function in the boar may be regulated by both estrogens and androgens. However, estrogen does not appear to play a major role in the regulation of these receptors. Immunocytochemistry for lactoferrin shows that lactoferrin is present in the corpus and cauda epididymis of boars aged 2 months to 2.5 years while the caput and testis are negative. These results indicate that lactoferrin is produced and secreted by the corpus and cauda where sperm maturation is occurring.
Impacts
With an increased understanding of the role steroids play in the epididymis, it will be possible to better evaluate the relationship between epididymal function and the fertilizing capacity of sperm in the ejaculate. It will also help in providing the steps necessary to improve the efficacy of cooled and frozen semen for artificial insemination.
Publications
- Pearl, C.A.,Berger, T. and Roser, J.F. 2005. Androgen and estrogen receptor expression in relation to steroid concentrations in the adult boar epididymis. (In prep.)
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Progress 01/01/04 to 12/31/04
Outputs
Epididymal tissue was processed for immunocytochemistry to localize estrogen and androgen receptors in boars from two until eight months of age and from adult animals ages one until two and a half years. Tissue was also processed for determination of steroid concentrations. In adult boars, androgen receptor and estrogen receptor beta are present in the principal cells of all three regions (caput, corpus, cauda). Estrogen receptor alpha is present in the principal cells of the caput, some cells in the corpus and not present in the cauda. Also in adult boars, the concentration of testosterone and estradiol are significantly higher in the testis compared with the epididymis (p < 0.001) but the epididymal regions are not significantly different from one another (p > 0.4). The lack of difference among the epididymal regions is surprising; however, this implies that estradiol and testosterone are equally available in the tissue to regulate all three epididymal regions.
These results support the hypothesis that estrogen in addition to androgen regulates epididymal function in the boar. These results were presented at the annual meeting of the Society for the Study of Reproduction in July of 2004. Determination of steroid concentrations and immunocytochemistry in boars aged two until eight months is currently underway. Immunocytochemistry for lactoferrin shows that lactoferrin is present in the corpus and cauda epididymis of boars aged 2 months to 2.5 years while the caput and testis are negative. These results indicate that lactoferrin is produced and secreted by the corpus and cauda where sperm maturation is occurring.
Impacts
With an increased understanding of the role steroids play in the epididymis, it will be possible to better evaluate the relationship between epididymal function and the fertilizing capacity of sperm in the ejaculate. It will also help in providing the steps necessary to improve the efficacy of cooled and frozen semen for artificial insemination.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
Epididymal and testicular tissue were processed for immunocytochemistry to localize estrogen and androgen receptors in boars from 1 wk to 8 mos of age. Preliminary analyses have confirmed that androgen and estrogen receptors are present in the testis and epididymis. In the adult boar testis, androgen receptors were found in Sertoli cells and estrogen receptor beta was localized in the germ cells. In the epididymis, androgen receptors were present in the principal cells of all three regions (caput, corpus, cauda) at all ages studied. Estrogen receptor alpha was found in the epidiydmis with a similar regional expression pattern as the androgen receptor. In studies conducted to date, estrogen receptor beta has also been found in the caput of adult boars. The successful demonstration of their presence in the reproductive tract of the boar is consistent with current concepts of receptor-mediated steroid regulation of testicular and epididymal function.
Impacts
With an increased understanding of the role steroids play in the epididymis, it will be possible to better evaluate the relationship between epididymal function and the fertilizing capacity of sperm in the ejaculate. It will also help in providing the steps necessary to improve the efficacy of cooled and frozen semen for artificial insemination.
Publications
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Progress 01/01/02 to 12/31/02
Outputs
To determine if two sex hormones called estrogens and andtrogens play a role in regulating the epididymis (the structure where sperm mature and are stored prior to ejaculation) in the boar. 1) To identify the site of androgen and estrogen action in the boar epididymis throughout sexual maturation. 2) To quantify the amount of androgen and estrogen present in the boar epididymis throughout sexual maturation. 3) To determine the role of testosterone and estrogen in regulating two important factors called lactoferrin and clusterin secreted by the boar epididymis.
Impacts
With an increased understanding of the role steroids play in the epididymis it will be possible to better evaluate the relationship between epididymal function and the fertilizing capacity of sperm in the ejaculate. It will also help in providing the steps necessary to improving the efficacy of cooled and frozen semen for artificial insemination.
Publications
- No publications reported this period
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