| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Regular article |
a Department of Physiology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
ABSTRACT
Bradykinin and a number of peptide hormones such as angiotensin, endothelin, and vasopressin stimulate anion secretion in rat epididymis via local formation of PGE2. These effects are mediated by cyclooxygenase (COX)-1 isozyme. The present study was undertaken to assess the androgen control of COX expression in the epididymis. Adult male Sprague-Dawley rats were bilaterally castrated through a scrotal route. Reverse transcription-polymerase chain reaction was used to measure COX-1 and COX-2 mRNAs in the epididymis in normal and castrated rats. Anion secretion in epithelia grown from the epididymides of these rats was studied by the short-circuit current technique. In normal rats, COX-1 and COX-2 mRNAs were detected in the intact epididymis. Elimination of spermatozoa by the technique of efferent duct ligation or flushing out spermatozoa did not affect the expression of either enzyme in the epididymis, indicating that the epithelium, but not spermatozoa, expressed the enzymes. Castration caused a time-dependent decrease in expression of COX-1 and COX-2 mRNAs, which were partially restored upon testosterone replacement. In epithelia cultured from castrated rats, there was a complete loss of bradykinin-induced anion secretion. This effect was reversible upon testosterone replacement. Although epithelia from castrated rats did not respond to bradykinin, they could respond to cAMP, forskolin, and PGE2 with only 20% loss of response magnitude when compared with epithelia from normal rats. These results suggest that the expression of COX-1 and COX-2 are dependent on androgen. The loss of COX-1 expression after castration correlates with the specific loss of anion secretion induced by bradykinin and possibly other hormones.
epididymis, signal transduction, testosterone
INTRODUCTION
Secretion of electrolytes (and fluid) in the epididymis is stimulated by bradykinin [1] and a number of vasoactive peptides [2–4]. These effects are abolished by nonsteroidal anti-inflammatory drugs (NSAIDs), suggesting the involvement of prostaglandin (PG) synthesis via cyclooxygenase (COX) as the mediator of the responses [1–4]. According to a proposed model [5], these peptides act on receptors on the basal cells to activate PLA2 with release of arachidonic acid (AA) from membrane phospholipids. AA is converted to PGG2 and PGH2 by COX-1 and then to PGE2 by the specific isomerase. PGE2 diffuses out of the cells and acts on the PG receptors, notably the EP2/4 subtypes, on the basolateral membrane of principal cells, to increase intracellular cAMP, which activates an apical anion channel (CFTR), resulting in secretion of anions and, secondarily, water. This model is based on evidence that 1) COX-1 specific inhibitors inhibit the lysylbradykinin (LBK)-stimulated anion secretion; 2) PGE2, but not the other COX products, mimicked the effect of LBK; 3) the effect of PGE2 is mediated through the cAMP-coupled EP2/4 receptors because its effect is reproduced by 11-deoxyl PGE1, a specific EP2/4 receptor agonist, but not by sulprostone, a specific EP1/3 receptor agonist; 4) COX-1 mRNA is expressed by intact rat epididymis and the COX-1 protein is localized mainly in basal cells [5]; 5) bradykinin caused PGE2 release from epididymal epithelia and, along with the bradykinin-induced anion secretion, can be blocked by COX-1 selective inhibitors (unpublished data). Through forming PGE2, COX-1 regulates anion and fluid secretion and optimize the milieu in which sperm are bathed. COX-2 is constitutively expressed by the principal cells of the intact epididymis and its physiological roles are obscure [5]. Little is known about the physiological regulation of the two isozymes. The present work investigated the effect of orchidectomy and testosterone replacement on the expression of COX-1 and COX-2 mRNA in the rat epididymis. A parallel study was also performed to delineate the functional consequences of changes in COX expression following castration and testosterone replacement.
MATERIALS AND METHODS
Epididymal Cell Culture for Short-Circuit Current Measurement
It has been shown that epididymides containing spermatozoa do not form monolayers in culture because spermatozoa prevent the plating of epithelial cells on filters [1]. Sperm-free epididymides from adult rats were used for forming epithelia for functional study. Efferent duct ligation was performed bilaterally on adult male Sprague-Dawley rats weighing about 350 g. Thirty days following the operation, the cauda epididymides were free of sperm. The sperm-free cauda epididymides were dissected out and used to culture epithelial monolayers, as described later. The epithelia so derived served as a control to epithelia from castrated rats. In some experiments, adult male rats were bilaterally castrated through a scrotal route. The epididymides were dissected out from rats 30 days after castration. They were used for epithelial cell culture, which is described later.
The cauda epididymides were cut into small pieces and placed in sterile Hanks balanced salt solution (HBSS) containing 0.25% trypsin. Tissues were incubated for 60 min at 32°C with vigorous shaking. The tissue was separated by low-speed centrifugation (800 x g for 5 min). The supernatant was discarded and the pellet resuspended in HBSS containing 0.1% collagenase for 120 min at 32°C with vigorous shaking. Cells were separated by centrifugation at 800 x g for 5 min. The pellet was resuspended in Eagles minimum essential medium (EMEM) containing nonessential amino acids (0.1 mM), sodium pyruvate (1 mM), glutamine (4 mM), 5
-dihydrotestosterone (1 nM), 10% fetal bovine serum (FBS), penicillin (100 IU/ml), and streptomycin (100 µg/ml). The pellet from epididymides of castrated rats was resuspended in EMEM containing all the ingredients except 5-dihydrotestosterone. The cell suspension was stored for 4 hr in a flask incubated at 32°C in 5% CO2 to eliminate smooth muscle cells and fibroblasts, which more than epithelial cells, had readily settled on the bottom of the flask. The epithelial cells in suspension were seeded into the wells of Matrigel-coated Milipore filter assemblies with a diameter of 0.2 cm2 floating in 15 ml of culture medium [6]. Thereafter, the monolayers reached confluency after 3 days in culture and were ready for the measurement of anion secretion using the short-circuit current (Isc) technique [6].
Measurement of Short-Circuit Current
Confluent epididymal monolayers were clamped between two halves of Ussing chambers with a 0.6 cm2 window and incubated on both sides with oxygenated (95% O2/5% CO2) Krebs-Henseleit solution maintained at 32°C. Epithelia were short-circuited by the use of a voltage clamp amplifier (DVC-1000; World Precision Instrument, New Haven, CT) [6]. The short-circuit current (Isc) was displayed continuously on a pen recorder (Kipp and Zonen, Pelft, The Netherlands). Transepithelial resistance was measured by transiently commanding the clamp to set the voltage at 0.2 or 0.4 mV away from zero. The resulting changes in transepithelial current allowed calculation of resistance using Ohm's law. Generally, confluent epithelia had a basal Isc of 1–2 µAcm-2 and a transepithelial resistance of 500 
cm2.
Drugs were added directly to the apical or basolateral side of the epithelium; the mixing time was only a few seconds. Basal Isc was measured after monolayers were allowed to equilibrate for 20 min. Responses to bradykinin, cpt-cAMP, PGE2, and forskolin were measured as changes in Isc at the peak of the response. Isc was expressed in microamperes per square centimeter area of the epithelium (µA/cm2).
Detection of COX-1 and COX-2 mRNAs in Epididymal and Sperm Cells by Reverse Transcription-Polymerase Chain Reaction
Reverse transcription-polymerase chain reaction (RT-PCR) was performed to detect expression of COX-1 and COX-2 in intact cauda epididymides from normal (sham-operated), castrated (at 5, 10, 20, and 30 days), efferent duct-ligated (at 30 days), and testosterone-replaced rats. Spermatozoa flushed out from the epididymis after cannulation of the epididymal tubules were also studied. The two primers used for amplifying COX-1 were 5'-TGGAGAAGTGCCAGCCCAACTCCC-3'; (sense primer corresponding to nucleotides 1584–1608) and 5'-GGGGCAGGTCTTGGTGTTGAGGCA-3' (antisense primer corresponding to nucleotides 1763–1789), which generated a COX-1 PCR product of 206 base pairs (bp). The two primers for COX-2 were 5'-CCCTCCCCACGTCCCTGAGCACCT-3' (sense primer corresponding to nucleotides 908–932) and 5'-GGTTTCAGGGAGAAGCGTTTGCGG-3' (antisense primer corresponding to nucleotides 1504–1480), which generated a 596-bp COX-2 PCR product. The ribosomal protein, S-16, was used as an endogenous control and coamplified in the PCR reactions. The two primers used for amplifying S-16 were 5'-TCCGCTTGCACTGGGCTTCAAGTCTT-3' (sense primer corresponding to nucleotides 15–38) and 5'-GCCAAACTTCTTCTTGGATTCGCAGCG-3' (antisense primer corresponding to nucleotides 376–399), which yielded an S-16 product of 385 bp. Total RNA was extracted from rat cauda epididymides and epididymal spermatozoa using TRIzol Reagent (Gibco BRL, Gaithersburg, MD). The quality and concentration of RNA was determined by gel electrophoresis and spectrophotometry at 260 nm. Two micrograms of tRNA and 1 µg of oligo(dT)-18 primer were denatured at 70°C for 5 min, annealed on ice for 5 min, then reverse transcribed to cDNA by SUPERSCRIPT II Rnase H-Reverse Transcriptase (Gibco BRL) in the presence of RNasin, 2 µl dithiothreitol (0.1 M), 2 µl deoxynucleoside triphosphates (10 mM each of dATP, dCTP, dGTP, and dTTP) in a final reaction volume of 20 µl for 50 min at 42°C. The reaction was terminated by heating to 70°C for 5 min. Complementary DNA (0.5 µg) was used as a template for performing PCR using the following parameters: denaturation at 94°C for 1 min, annealing at 52°C for 1 min, and extension at 72°C for 1 min. A total of 25 cycles were performed. Under these conditions, the amplification of both the target gene and S-16 were in the linear range as demonstrated in a series of preliminary experiments by removing samples for analysis at cycles 20, 22, 24, 25, 27, 29, and 30. An aliquot of 8 µl was withdrawn from each PCR reaction tube, resolved in 1.2% agarose gels in 0.5x TBE buffer (45 mM Tris, 45 mM boric acid, 1 mM EDTA; pH 8.0), and visualized by ethidium bromide. The authenticity of the COX-1 and COX-2 PCR products were confirmed by nucleotide sequencing (ABI PRISM 310 Genetic Analyzer; Perkin Elmer, Framingham, MA). Bands were quantified by densitometry (Molecular Dynamics, Amersham Pharmacia Biotech AB, Uppsala, Sweden; model PDS-1P90, ImageQuaNT v 4.2 software). COX-1 and COX-2 mRNA expressions were normalized against S-16 expression detected in the same PCR reaction. COX-1 and COX-2 expressions at various times after castration and following hormone replacement were expressed as a percentage of controls (efferent duct-ligated epididymides). A negative control with no template was always included in each PCR step.
Castration and Hormonal Replacement
Adult male Sprague-Dawley rats were bilaterally castrated [7]. Surgical procedures were performed under sterile conditions. Sodium pentobarbitone (50 mg/kg body weight, i.p.) was employed to anesthetize the animals. The efferent ducts and the testicular vessels were ligated close to the testes, which were then removed. The epididymides were returned to the scrotum and the incisions closed with silk sutures. The animals were allowed to recover but were killed after 5, 10, 20, or 30 days (eight rats in each group) by asphyxiation with increasing concentrations of CO2. The cauda epididymides were weighed and prepared for epithelial monolayer culture as described earlier. For RT-PCR study, the cauda epididymides were washed with PBS and stored at -80°C until use. Another group of 12 rats were castrated in a similar manner; however, after 10 days, they were i.m. injected with testosterone proprionate (2 mg/kg per day [7, 8]) suspended in sesame oil for a further 20 days. These animals constituted the "hormone replacement" group. In another group of 12 rats, the testes and epididymides were pulled out and returned to the scrotum. These sham-operated animals served as controls.
Efferent Duct Ligation
Efferent duct ligation was performed bilaterally through an abdominal route. Sodium pentobarbitone (50 mg/kg body weight, i.p.) was used as anesthetic. The efferent ducts were ligated with silk sutures close to the testes. Care was taken not to damage any testicular blood vessels. The testes was then placed back in the scrotal sac and rats were allowed to recover. Thirty days after surgery, the epididymides appeared healthy except that the lumens were clear of sperm. These animals served as controls to the castrated rats for Isc measurement.
Microperfusion of Rat Cauda Epididymis
Adult male Sprague-Dawley rats weighing 350–450 g were anesthetized with sodium pentobarbitone (50 mg/kg body weight, i.p.) as described earlier. The contents from both cauda epididymides were collected after cannulation of the epididymal ducts and the vas deferens as described previously [9]. Normal Krebs-Henseleit solution was perfused into the lumen of the epididymis using a Harvard infusion pump, displacing the spermatozoa into a calibrated polythene tubing inserted into the vas deferens.
Solutions and Drugs
Krebs-Henseleit solution used in the Isc study had the following composition (mM): NaCl, 118; KCl, 4.7; CaCl2, 2.5; MgSO4, 1.8; KH2PO4, 1.8; NaHCO3, 25.0; and glucose, 14.0. This solution had a pH of 7.3–7.4 when bubbled with 95% O2/5% CO2. EMEM, FBS, and nonessential amino acids were purchased from Gibco Laboratories. Penicillin/streptomycin, HBSS, sodium pyruvate, trypsin, collagenase I, forskolin, cpt-cAMP, PGE2, and sesame oil were from Sigma (St. Louis, MO). LBK was from RBI Research Biochemicals (Natick, MA). Testosterone was from Fluka (Buchs, Switzerland). Matrigel was purchased from Collaborative Biochemical Products (Bedford, MA). Stock solutions of these agents were made in distilled water, except PGE2, which was dissolved in ethanol. In all cases, addition of solvent alone to epithelia did not affect Isc.
Statistical Evaluation
Values were given as the mean ± SEM of 8 to 12 independent experiments. Data were analyzed by ANOVA followed by Bonferroni t-test with the help of the CSS statistical software package (StatSoft, Inc, Tulsa, OK). P < 0.05 was considered statistically significant.
RESULTS
Organ Weight
There was a time-dependent decrease in the weight of the cauda epididymides after castration. Thirty days after castration, the weight of cauda epididymides was reduced to 42.8% ± 1.7% (n = 12 rats) of sham-operated controls. In castrated rats supplemented with testosterone, the weight of the cauda epididymides was 68.5% ± 3.3% (n = 12 rats) of sham-operated controls. In rats with efferent ducts that had been ligated for 30 days, the cauda weight was reduced to 91.2% ± 1% (n = 12 rats) of sham-operated controls.
Expression of COX Isozymes Before and After Androgen Withdrawal
Cauda epididymides from adult rats were found to express both COX-1 and COX-2 isozymes. The signal appeared to be from the epithelium because sperm-free epididymides obtained from efferent duct ligation or by flushing out spermatozoa in situ yielded COX-1 and COX-2 RT-PCR products, whereas spermatozoa flushed out from epididymides did not (Figs. 1 and 2). Rats were castrated at 5, 10, 20, or 30 days and the expressions of COX-1 and COX-2 mRNAs were studied. The expression levels were normalized by S-16 expression detected in the same PCR reaction, and these values were compared with those of control intact-epididymides (Fig. 3). After castration, there was no change in the expression levels of S-16; however, castration caused a time-dependent decrease in both COX isozymes (Figs. 1–3). Total loss of COX-1 gene expression was noted on Day 30 after castration. In contrast, COX-2 gene expression was more sensitive to androgen ablation. Expression of COX-2 was undetectable on Day 5 postcastration. The authenticity of these PCR products was verified by direct nucleotide sequencing (data not shown).
|
|
Effect of Testosterone Replacement on the Gene Expression of COX-1 and COX-2
COX-1 and COX-2 gene expression was not detected in the cauda after 30 days postcastration (Fig. 1, lane 8; Fig. 2, lane 8; Fig. 3). A group of rats was castrated at 10 days and then injected with testosterone propionate (2 mg/kg body weight) for the next 20 days. RT-PCR study revealed partial restoration of COX-1 and COX-2 mRNA signals after hormone replacement (Fig. 1, lane 9; Fig. 2, lane 9; Fig. 3).
|
Effect of Castration on the Induction of Isc by Bradykinin
Anion secretion stimulated by LBK was tested in epithelia cultured from 30-day-castrated and testosterone-replaced rats. Cauda epididymides free of spermatozoa were obtained from rats in which efferent ducts had been ligated 30 days before. The epithelia cultured from these epididymides were used as controls. Epithelia were incubated in normal Krebs-Henseleit solution and stimulated with 0.1 µM LBK added apically or basolaterally (Fig. 4). LBK application to the apical or basolateral side resulted in a stimulation of inward current, which has been proven to be the result of anion secretion [1, 5]. After castration, the anion secretory response to basolateral addition of LBK was abolished, but the response to apical application was only slightly reduced (Figs. 4 and 5). Upon replacement with testosterone, the response to basolateral LBK was restored toward normal.
|
Anion Secretion Induced by cAMP, Forskolin, and PGE2 in Castrated Rat Epididymal Epithelia
Previous work has suggested that the bradykinin-stimulated anion secretion is mediated by PGE2, which is formed from AA by COX-1 in the basal cells. PGE2 acts on the prostaglandin EP2/4 receptors on principal cells to increase intracellular cAMP, which then activates apical CFTR, resulting in secretion of anion and, secondarily, water [5]. It would be of interest to see if castration affects the responses of the epithelium to PGE2, forskolin (activator of adenylate cyclase), and cAMP. The results are shown in Figure 6. Although epithelia from castrated rats did not respond to basolateral bradykinin (0.1 µM), they could respond to cAMP (100 µM), forskolin (10 µM), and PGE2 (1 µM) with only a 20% loss of response magnitude when compared with epithelia from normal mature rats (Figs. 6 and 7).
|
DISCUSSION
Although the epithelium lining the epididymis is known to play an active role in forming a specialized fluid environment conducive to sperm maturation and storage, our understanding of the regulation of electrolyte and fluid transport in the epididymis remains largely incomplete. The prime regulator of epididymal functions is dihydrotestosterone, the 5-reduced metabolite of testosterone [10]. Although the dependence on androgen of protein secretion [11–15], cellular enzyme activities [16–19], and hormone receptor expression [20, 21] in the epididymis has been well-documented, only one report has ever been made on the androgen control of sodium and fluid transport in the epididymis [7].
In the epididymis, secretion of electrolytes and fluid is regulated by neurohumoral factors that act in a timely and concerted manner to bring about the formation of a correct fluid microenvironment for spermatozoa. Bradykinin [1], angiotensin [2], endothelin [3], vasopressin [4], and 5-hydroxytryptamine [22] stimulate anion secretion through the formation of prostaglandins. This process requires COX-1 isozyme, which is expressed by basal cells [5]. The prostaglandins that are formed diffuse into the interstitial space and act on the prostaglandin EP2/4 receptors on the basal membrane of principal cells. This leads to the formation of cAMP, which then activates the opening of the apically placed CFTR, leading to secretion of anions. NSAIDs inhibit COX, abolish the formation of prostaglandins and, consequently, the stimulation of electrolyte and fluid secretion by the peptides. The COX-1 isozyme is expressed by basal cells of epididymal epithelium, whereas COX-2 is detected in principal cells of intact epididymis under conditions not known to be associated with inflammation [5]. It was concluded from these studies that COX-1 plays an important role in the regulation of electrolyte and water secretion by the epididymis, while the function of COX-2 remains obscure at present. Recently, COX-2 has been shown to be the predominant COX isoform in the epithelium of the distal vas deferens, where constitutive expression of COX-2 is several times greater than in any other organs of the body [23]. Evidence is accumulating that COX-2 plays a role in the regulation of physiological processes other than mediating inflammation [24].
RT-PCR study has confirmed previous results that COX-1 and COX-2 isoforms are expressed by the epididymis. The signals came mainly from the epithelium and not the sperm because eliminating spermatozoa from the lumen of the intact epididymis by the technique of efferent duct ligation or flushing out sperm from the epididymal tubule did not affect the expression level in the sperm-free cauda epididymis (Figs. 1 and 2). Castration caused a decrease of COX-1 and COX-2 mRNAs. For COX-1, the effect was gradual: a decrease was seen on Day 5 after castration and the signal was undetectable on Day 30; however, the signal partially recovered upon testosterone replacement (Figs. 1 and 3). COX-2 mRNA expression showed a more rapid decline. The signal was undetectable on Day 5 postcastration and remained so for longer periods after castration. As with COX-1, the signal partially reappeared upon testosterone replacement (Figs. 2 and 3). The lack of a significant effect of efferent duct ligation on COX-1 and COX-2 expression may be taken to indicate that the expression of the enzymes are not dependent on luminal factors flowing down from the testis.
The loss of expression of COX-1 mRNA correlated with a loss of anion secretion induced by basolateral bradykinin; the response to apical response, however, was only slightly reduced (Figs. 5 and 6). The results are consistent with a previous observation that formation of PGE2 via COX-1 is responsible for the stimulation of anion secretion by bradykinin acting from the basolateral side (through basolateral bradykinin BK2 receptors [5]). Recently, it has also been shown that the secretory response to bradykinin acting from the apical side (on apical bradykinin BK2 receptors) is mediated through a COX-independent pathway and did not involve synthesis of prostaglandins (unpublished data). This can explain the preservation of the response to apical bradykinin after castration (Figs. 5 and 6). The loss of anion secretion induced by basolateral bradykinin was readily reversible by hormone replacement, as was COX-1 expression.
|
It could be argued that the loss of response to bradykinin upon castration was due to a general regression of the epithelium because androgens are required for the maintenance of normal epididymal morphology and functional integrity [10]. We have studied the effects of exogenous PGE2, forskolin, and cAMP on anion secretion in the epididymides from normal and castrated rats. These three agents work on some intermediary steps along the pathway of induction of anion secretion by basolateral bradykinin [5]. It was found that the responses to these agents were reduced by 20% after testosterone withdrawal compared with those of control rats. The results suggest that the loss of secretory response to basolateral bradykinin after castration is not attributed to a general regression of the epithelium but to specific ablation of COX-1 activity. However, the results could not preclude a concomitant loss of basolateral bradykinin receptors after testosterone withdrawal.
In conclusion, this work has provided evidence that COX-1 and COX-2, which are the key enzymes in the synthesis of prostaglandins, are controlled by testicular androgens. COX-1 mediates the stimulation of epididymal anion (and hence fluid) secretion by neurohumoral factors, whereas the role of COX-2, which is constitutively expressed in the epididymis, remains unknown. Androgen regulates the formation of the epididymal microenvironment through regulation of COX-1.
|
FOOTNOTES
First decision: 29 March 2000.
1 This work was supported by the Research Grant Council (earmarked research grant CUHK4293/99M), the International Consortium on Male Contraception, and the Chinese University of Hong Kong. 
2 Correspondence. FAX: 852 2603 5022;patrickwong{at}cuhk.edu.hk
Accepted: April 19, 2000.
Received: January 13, 2000.
REFERENCES
This article has been cited by other articles:
|
|
 |
|
  W. R. Winnall, U. Ali, M. K. O'Bryan, J. J. Hirst, P. A.F. Whiley, J. A. Muir, and M. P. Hedger Constitutive Expression of Prostaglandin-Endoperoxide Synthase 2 by Somatic and Spermatogenic Cells Is Responsible for Prostaglandin E2 Production in the Adult Rat Testis Biol Reprod, May 1, 2007; 76(5): 759 - 768. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Mewe, C. K. Bauer, J. R. Schwarz, and R. Middendorff Mechanisms Regulating Spontaneous Contractions in the Bovine Epididymal Duct Biol Reprod, October 1, 2006; 75(4): 651 - 659. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Mewe, C. K. Bauer, D. Muller, and R. Middendorff Regulation of Spontaneous Contractile Activity in the Bovine Epididymal Duct by Cyclic Guanosine 5'-Monophosphate-Dependent Pathways Endocrinology, April 1, 2006; 147(4): 2051 - 2062. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Shibata, B. Kashiwagi, S. Arai, Y. Fukabori, K. Suzuki, S. Honma, and H. Yamanaka Direct Regulation of Prostate Blood Flow by Vascular Endothelial Growth Factor and Its Participation in the Androgenic Regulation of Prostate Blood Flow in Vivo Endocrinology, October 1, 2004; 145(10): 4507 - 4512. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. R. Chauvin and M. D. Griswold Androgen-Regulated Genes in the Murine Epididymis Biol Reprod, August 1, 2004; 71(2): 560 - 569. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Ezer and B. Robaire Gene Expression Is Differentially Regulated in the Epididymis after Orchidectomy Endocrinology, March 1, 2003; 144(3): 975 - 988. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. K. Rao, C. M. Wayne, and M. F. Wilkinson Pem Homeobox Gene Regulatory Sequences That Direct Androgen-dependent Developmentally Regulated Gene Expression in Different Subregions of the Epididymis J. Biol. Chem., December 6, 2002; 277(50): 48771 - 48778. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Jaleel, R. M. London, S. L. Eber, L. R. Forte, and S. S. Visweswariah Expression of the Receptor Guanylyl Cyclase C and Its Ligands in Reproductive Tissues of the Rat: A Potential Role for a Novel Signaling Pathway in the Epididymis Biol Reprod, December 1, 2002; 67(6): 1975 - 1980. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B.L.Y. Cheuk, S.B. C. Chew, R.R. Fiscus, and P.Y.D. Wong Cyclooxygenase-2 Regulates Apoptosis in Rat Epididymis Through Prostaglandin D2 Biol Reprod, February 1, 2002; 66(2): 374 - 380. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
