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The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 62:1346-1351 (2007)
© 2007 The Gerontological Society of America

Effect of Aging on the Expression of Adrenomedullin and Its Receptor Component Proteins in the Male Reproductive System of the Rat

Yuk-Yin Li, Wai-Sum O and Fai Tang

Departments of 1 Physiology, 2 Anatomy, 3 Centre of Reproduction, Development and Growth, 4 Centre of Heart, Brain, Hormone and Healthy Aging, Faculty of Medicine, The University of Hong Kong, China.

Address correspondence to Fai Tang, PhD, Department of Physiology, Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong, China. E-mail: ftang{at}hkucc.hku.hk


   Abstract
Top
 Abstract
Materials and Methods
 Results
 Discussion
 References
 
This study investigated the levels of adrenomedullin (AM) and the gene expression of AM, calcitonin receptor-like receptor (CRLR), receptor activity-modifying proteins (RAMPs), and receptor-coupling protein (RCP) in the testis, ventral prostate, seminal vesicle, and epididymis in rats aged 3, 12, and 20 months by radioimmunoassay and semiquantitative reverse transcription–polymerase chain reaction (RT–PCR). The results indicate an age-related increase in AM and its messenger RNA (mRNA) levels in the testis and decrease in the sex accessory glands. The gene expression of CRLR and RCP decreased only in the sex accessory glands. The changes in the gene expression of RAMPs suggest that the major increase was in CGRP receptors in the testis, whereas the major deceases in the ventral prostate and the seminal vesicles might be CGRP and AM receptors, respectively. The decreases in these receptors were similar in the epididymis. The results suggest possible roles of AM in the male reproductive system during aging.

ADRENOMEDULLIN (AM) is a multifunctional peptide with a long-lasting vasorelaxant activity first isolated from pheochromocytoma (1). Human and rat AM consists of 52 and 50 amino acids, respectively (2,3). AM belongs to the calcitonin superfamily of peptides and has a conserved six-amino acid ring formed by an intramolecular disulphide bond and a C-terminal amide (4). AM can bind to the calcitonin gene-related peptide (CGRP) receptor in several types of tissues (5,6). However, specific AM receptors that are insensitive to CGRP receptor antagonist, CGRP(8-37), have been identified (7). McLatchi and colleagues (8) reported that the calcitonin receptor-like receptor (CRLR) accounts for the majority of AM and CGRP binding, and whether it binds to AM or CGRP depends on the type of receptor activity-modifying protein (RAMP) that is expressed, namely RAMP1, RAMP2, or RAMP3. CRLR combines with RAMP1 and RAMP2 to give rise to a specific CGRP receptor and a specific AM (AM1) receptor, respectively. The combination of CRLR with RAMP3, however, will result in a receptor (AM2 receptor) that binds both AM and CGRP (9,10). A functional AM or CGRP receptor also requires an intracellular protein, receptor-coupling protein (RCP), for signal transduction (11).

Immunoreactive AM and its messenger RNA (mRNA) have been identified in various tissues both in the human and the rat, including the neuroendocrine, cardiovascular, digestive, and respiratory systems (2,3,12–16). The gene expression and/or peptide of AM have also been shown in reproductive organs such as the ovary (16,17), uterus (16,18), testis (15,19), prostate (20,21) and epididymis (22).

There are several age-associated decreases in the human male reproductive system including sperm motility, testicular perfusion, and numbers of Sertoli cells and Leydig cells, with an associated decrease in serum testosterone (23). These age-related changes are suggested to be caused by functional alterations in the reproductive organs and the endocrine system (24). We recently found that AM suppresses human chorionic gonadotropin (hCG)-stimulated testosterone secretion (19) besides inhibiting endothelin-1 (ET-1)-induced contraction of peritubular myoid cells in the seminiferous tubules (25). AM concentrations are much higher in the human seminal plasma than in the serum (26). AM is also expressed and regulated by androgen in the ventral prostate epithelial cells (20). These findings suggest that AM may have potential roles in modifying the androgen secretion and in regulating the functions of the male reproductive system.

In the present study, we have determined the levels of AM and its mRNA as well as the gene expression of its receptor components in the testis, ventral prostate, seminal vesicle, and epididymis in an attempt to understand its possible roles in the male reproductive system during aging.


   MATERIALS AND METHODS
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 Abstract
 Materials and Methods
Results
 Discussion
 References
 
Animals
Male Sprague-Dawley rats of 3, 12, or 20 months of age were obtained from the Laboratory Animal Unit, Faculty of Medicine, The University of Hong Kong. All procedures had been approved by the Committee on the Use of Live Animals for Teaching and Research of the Faculty of Medicine, and were carried out in accordance with the Guide for the Care and Use of Laboratory Animals (National Academy of Sciences).

Extraction of AM From the Reproductive Tissues and the Plasma
Tissues including testis, ventral prostate, seminal vesicle, and epididymis of eight rats from each age group were used, and each tissue was homogenized in 2 N acetic acid, then boiled for 10 minutes. A 50 µL aliquot was taken for protein assay, and the remaining homogenates were centrifuged at 18,600 x g for 20 minutes at 4°C (Sorvall SM 24; Thermo Fisher Scientific, Inc., Waltham, MA). The supernatants were lyophilized and stored at –20°C until assay.

A volume of 2 mL of plasma was acidified with an equal volume of 1% trifluoroacetic acid (TFA) and centrifuged at 18,600 x g for 20 minutes at 4°C (12). The diluted plasma samples were loaded onto pre-equilibrated C-18 Sep-columns (Waters Corp., Milford, MA), which were then washed twice with 3 mL of 1% TFA. The peptide was eluted with 60% high-performance liquid chromatography (HPLC) grade acetonitrile in 1% TFA, dried in a speed-vacuum concentrator (Savant, Farmingdale, NY), redissolved in 0.5 mL of radioimmunoassay (RIA) buffer (0.1% sodium phosphate [pH 7.4], 0.1% heat-inactivated bovine serum albumin [BSA], 0.05 M sodium chloride, 0.01% sodium azide, and 0.1% Triton X-100), and further purified with a nanospin column (Millipore Corp., Benford, MA; molecular weight cutoff point is 10 kd) (13).

RIA
The lyophilized tissue sample was reconstituted in RIA buffer for the determination of immunoreactive AM concentration (12). Rat AM and AM antiserum were purchased from Peninsula (Belmont, CA). The 125I-labeled AM was obtained from Phoenix (Belmont, CA). The sensitivity for the assay was 5 pg/tube. The intraassay and interassay coefficients of variation were 7% and 10%, respectively.

Protein Measurement
Aliquots (50 µl) of tissue homogenate or standard (BSA) were boiled with 1 N NaOH for 10 minutes, and 50 µL of the boiled sample was mixed with 2.5 mL of protein assay reagent (Bio-Rad, Hercules, CA). After 10 minutes of incubation at room temperature, the samples were measured spectrophotometrically at 595 nm (LKB Ultraspec II; Biochrom, Cambridge, U.K.). The immunoreactive AM was expressed as femtomoles per milligram of protein.

RT–PCR of AM, CRLR, RAMP, and RCP
Total RNA of the testis and the sex accessory glands was prepared using TRIZOL reagent (22) and subjected to RT–PCR (19). RNA samples (5 µg) were reverse-transcribed into complementary DNA (cDNA) with SuperScript II reverse transcriptase according to the manufacturer's instructions (Life Technologies, Carlsbad, CA). The mRNA levels of AM, CRLR, RAMP, β-actin, or L19 were then measured by PCR using HotStarTaq DNA polymerase (Qiagen, Valencia, CA) with the corresponding forward and reverse primers. The primers were designed on the basis of the published sequence of AM (ttcagcagggtatcggagc-forward; ccgactgttcaatgctgcc-reverse); CRLR (ccaaacagacttgggagtcactagg-forward; gctgtcttctctttctcatgcgtgc-reverse); RAMP1 (cactcactgcaccaaactcgtg-forward; cagtcatgagcagtgtgaccgtaa-reverse); RAMP2 (aggtattacagcaacctgcggt-forward; acatcctctgggggatcggaga-reverse); RAMP3 (acctgtcggagttcatcgtg-forward; acttcatccggggggtcttc-reverse); RCP (agaacttgaacgccatcacc-forward; ccatcagctggatctcaaca-reverse); β-actin (ggaaatcgtgcgtgacatta-forward; aggaaggaaggctggaagag-reverse); and L19 (gaaatcgccaatgccaactc-forward; accttcaggtacaggctgtg-reverse). The PCR condition for AM was 94°C for 15 minutes and cycles of 94°C for 1 minute, 56°C for 1 minute, and 72°C for 1 minute (33 cycles for testis, 35 cycles for ventral prostate and seminal vesicle, and 36 cycles for epididymis). The PCR conditions for CRLR and RAMP were 94°C for 15 minutes followed by cycles of 94°C for 30 seconds, 60°C for 30 seconds, and 72°C for 90 seconds (for testis: 30 cycles for CRLR and RAMP2, 26 for RAMP1, 34 for RAMP3; for ventral prostate: 32 cycles for CRLR, RAMP1, RAMP2, and RAMP3; for seminal vesicle: 28 cycles for CRLR, 32 for RAMP1 and RAMP2, 39 for RAMP3; for epididymis: 32 cycles for CRLR and RAMP1, 35 for RAMP2, 37 for RAMP3). The condition for RCP was 94°C for 15 minutes and cycles of 94°C for 1 minute, 63°C for 1 minute, and 72°C for 1 minute (26 cycles for testis, 33 cycles for ventral prostate, 31 cycles for seminal vesicle, and 32 cycles for epididymis). The condition for β-actin was 94°C for 15 minutes and 28 cycles of 94°C for 45 seconds, 59°C for 30 seconds, and 72°C for 45 seconds. The condition for L19 was 94°C for 15 minutes and 34 cycles of 94°C for 30 seconds, 56°C for 30 seconds, and 72°C for 1 minute. The PCR products were analyzed on a 1.5% agarose gel with ethidium bromide at 0.5 µg/mL using a gel documentation and analysis software (GeneGenius; Syngene Co., Cambridge, U.K.). The mRNA expression level of the test gene was expressed in arbitrary units after normalizing the band intensity with that of the corresponding β-actin or L19 internal control. For all RT–PCR protocols, there were linear relationships between the amounts of cDNA and the optical densities of the band, confirming the reliability of the RT–PCR assay for the quantification of the mRNA levels. The identities of all the PCR products were confirmed by gene sequencing (Genome Centre, Faculty of Medicine, The University of Hong Kong).

Plasma Testosterone Measurement by Enzyme Immunoassay
Plasma levels of testosterone were measured according to the manufacturer's instructions with a testosterone immunoassay kit (Diagnostic Systems Laboratories Inc., Webster, TX). The intraassay and interassay coefficients of variation were 5.6% and 4.2%, respectively.

Statistical Analysis
All data are expressed as mean ± standard error of the mean, and statistical significance assessed by one-way analysis of variance (ANOVA) followed by Student–Newman–Keuls (SNK) test for post hoc comparisons, with p <.05 taken as significant.


   RESULTS
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Discussion
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The plasma levels of testosterone were 3.26 ± 0.84, 1.15 ± 0.27, and 1.67 ± 0.2 ng/mL in the young, middle-aged, and old rats, respectively. They were about two- to threefold lower in middle-aged and old groups as compared with the young group.

The body weights and the levels of AM in the rat testis, ventral prostate, seminal vesicle, and epididymis among the three age groups were summarized in Table 1. The body weights were significantly increased with age and were almost doubled at old age. Both plasma and testicular AM levels were significantly increased in both middle and old groups. In contrast, in the ventral prostate, AM level was decreased in the old group. The AM levels in the seminal vesicle and epididymis were also reduced in both middle-aged and old groups (Table 1).


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  		Table 1. Body Weight and Adrenomedullin (AM) Levels in the Plasma, Testis, Ventral Prostate, Seminal Vesicle, and Epididymis Among Young, Middle-Aged, and Old Rats.

 
The mRNA expression of AM and its receptor components were estimated by semiquantitative RT–PCR, and the results are shown in Figures 1–4GoGoGo. The mRNA levels of testicular AM, RAMP1, and RAMP3 were significantly upregulated in the old group as compared with both young and middle-aged groups (Figure 1). The levels of CRLR, RAMP2, and RCP were not affected by aging. In the ventral prostate, the AM mRNA levels were significantly reduced in the old group as compared with the young (Figure 2). The mRNA expressions of RAMP1 and RCP were down-regulated in both middle and old groups. However, both CRLR and RAMP2 mRNA expressions were unaffected with aging. The mRNA levels of AM, CRLR, RAMP2, and RAMP3 were decreased in both middle-aged and old groups in the seminal vesicle (Figure 3). In addition, RCP mRNA expression was significantly diminished in the old group, whereas there was no significant change in the RAMP1 mRNA level among the three age groups. Ribosomal protein L19 was used as internal control for the determination of the changes in mRNA expression in epididymis because it is a better housekeeping gene in this tissue. All the mRNA levels being studied were significantly decreased in the epididymis in both middle-aged and old groups (Figure 4).


Figure 01
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  		Figure 1. Messenger RNA (mRNA) expression levels of adrenomedullin (AM), calcitonin receptor-like receptor (CRLR), receptor-coupling protein (RCP) (A), and receptor activity-modifying proteins (RAMPs) (B) in testis among young, middle-aged, and old rats. Values represent the means ± standard error of 8 rats in each group, and are expressed in arbitrary units. **p <.01, ***p <.001 versus the young group

 

Figure 02
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  		Figure 2. Messenger RNA (mRNA) expression levels of adrenomedullin (AM), calcitonin receptor-like receptor (CRLR), receptor-coupling protein (RCP) (A), and receptor activity-modifying proteins (RAMPs) (B) in the ventral prostate among young, middle-aged, and old rats. Values represent the means ± standard error of 7 rats in each group, and are expressed in arbitrary units. *p <.05, **p <.01, ***p <.001 versus the young group

 

Figure 03
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  		Figure 3. Messenger RNA (mRNA) expression levels of adrenomedullin (AM), calcitonin receptor-like receptor (CRLR), receptor-coupling protein (RCP) (A), and receptor activity-modifying proteins (RAMPs) (B) in the seminal vesicle among young, middle-aged, and old rats. Values represent the means ± standard error of 8 rats in each group, and are expressed in arbitrary units. *p <.05, **p <.01, ***p <.001 versus the young group

 

Figure 04
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  		Figure 4. Messenger RNA (mRNA) expression levels of adrenomedullin (AM), calcitonin receptor-like receptor (CRLR), receptor-coupling protein (RCP) (A), and receptor activity-modifying proteins (RAMPs) (B) in the epididymis among young, middle-aged, and old rats. Values represent the means ± standard error of 8 rats in each group, and are expressed in arbitrary units. *p <.05, **p <.01, ***p <.001 versus the young group

 

   DISCUSSION
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 Abstract
 Materials and Methods
 Results
 Discussion
References
 
The present study demonstrates the presence of both AM peptides and AM mRNA in the rat testis, ventral prostate, seminal vesicle, and epididymis as well as the age-associated changes of AM and its mRNA levels in these tissues. The presence of AM and its receptor components in the same tissues suggest the autocrine/paracine action of AM in the male reproductive system. There is excellent agreement between the changes in AM level and gene expression except for the testis, in which the peptide levels increased significantly both in 12-month-old and 20-month-old rats, whereas the increase in AM mRNA was only borderline in the 12-month-old rats and greatly elevated in 20-month-old rats.

Both AM and its mRNA levels are increased with age in the testis. As AM has been found to inhibit hCG-stimulated testosterone production (19), this age-related increase in AM is in line with the age-related reduction in circulating testosterone concentrations. However, because the decrease in serum testosterone levels precedes the major increase in AM gene expression, the contribution of AM to the change in testosterone production remains unclear. Indeed, the main factor for the decrease in serum testosterone with age is the age-related decrease in plasma luteinizing hormone (LH) level (27,28). It is known that the basal LH level decreases and the basal follicle-stimulating hormone (FSH) level remains unchanged (29) in the old Sprague-Dawley rat, although the latter was increased in the old Brown Norway rat (28). FSH and hCG have been found to inhibit AM gene expression and secretion in rat Leydig cells and Sertoli cells, respectively (Chan YF, 2006, personal communication). The decrease in serum LH level and the increase in Leydig cell number (27) may be some of the causes for the increase in AM gene expression and secretion in the testis of the old rats in this study. In addition to the effect of AM on steroidogenesis, there may be an age-related decrease in the contraction of seminiferous tubules as AM is able to antagonize ET-1-induced contraction of testicular peritubular myoid cells (25). It seems that the binding and response to CGRP would be more affected as there were increases in RAMP1 and RAMP3, both of which when combined with CRLR will generate receptors that bind CGRP.

The levels of AM and its mRNA as well as the mRNA levels of receptor components are all decreased in the secondary sex organs studied here: ventral prostate, seminal vesicle, and epididymis. AM is expressed mainly in the secretory cells of the ventral prostate epithelium and is androgen dependent (20,21). Therefore, the age-related decrease in AM and its mRNA levels in ventral prostate may be due to the reduction of circulating testosterone concentrations. It has been demonstrated that AM causes a relaxation of the smooth muscle in the rat prostate (30) and increases prostatic blood flow (31); therefore, reduction of AM with age may affect the secretion and motility of the gland. As in the testis, the change in the gene expression of the receptor component proteins was mainly in RAMP1, suggesting a possible decrease in binding and response to CGRP, although there was also a slight decrease in CRLR gene expression. The reduction of RCP expression is prior to that of AM expression, suggesting that the response to AM may be already impaired at middle age.

There are age-related decreases in the gene expression of AM, CRLR, RAMP2, and RAMP3, but not in RAMP1 in the seminal vesicle. This finding suggests that the decrease in binding and response to AM may be greater than that for CGRP. The decrease in AM production in the ventral prostate and seminal vesicle may give rise to a reduction of AM concentration in the seminal fluid. Like calcitonin (32), AM concentration is much higher in seminal fluid than in the plasma and is positively related to sperm motility (26). These findings, together with the presence of calcitonin (33) and high-affinity calcitonin-binding sites (34) in human spermatozoa, suggest a possible role of AM in regulating sperm motility. Indeed Chiu and colleagues (Chiu PC, Yeung WS, Ho PC, 2006, personal communication) have found a stimulatory effect of AM on human sperm motility. The decrease in AM production observed here in seminal vesicle and prostate may account for the reduced sperm motility with age reported previously (24). This hypothesis requires further investigation.

We previously demonstrated that AM is present in the epithelial cells of the epididymis and is able to stimulate anion transport (22). The age-associated decrease in epididymal AM may impair the secretory activity of the epididymis and thereby affect the maturation of sperm. The gene expression of all receptor components is down-regulated in middle and old ages, which suggests a decrease in binding and response to both AM and CGRP.

Conclusion
Adrenomedullin and the gene expression of its receptor components are differentially regulated in primary and secondary sex organs. The first point of interest is both AM and its mRNA levels are increased in the testis with age, whereas they are decreased with age in the ventral prostate, seminal vesicle, and epididymis. It is pertinent to note that the increase in gene expression occurs in the testes of old rats, whereas the decreases in gene expression in the sex accessory glands are found in both middle-aged rats and old rats. This finding suggests that, although the changes in the sex accessory glands may be responses to the age-related decreases in serum testosterone levels, the increases in gene expression in the testis may not be important for the decline in testosterone production (which indeed it is not). The second point of interest is the different responses in the gene expression of receptor component proteins in different organs. Although both CGRP and AM receptors seem to be equally affected in the epididymis, AM receptors are more affected in the seminal vesicles, and CGRP receptors are more affected in the testis and the ventral prostate. The explanation for this as well as the significance awaits further clarification.


   Acknowledgments
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 Results
 Discussion
 References
 
The work described in this article was partially supported by a grant from the Reserch Grant Council of the Hong Kong Special Administrative Region, China (HKU 7451/04M).


   Footnotes
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Decision Editor: Huber R. Warner, PhD

Received January 10, 2007

Accepted July 11, 2007


   References
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 Materials and Methods
 Results
 Discussion
 References
 

  1. Kitamura K, Kangawa K, Kawamoto M, et al. Adrenomedullin: a novel hypotensive peptide isolated from human pheochromocytoma. Biochem Biophys Res Commun. 1993;192:553-560.[Medline]
  2. Kitamura K, Sakata J, Kangawa K, Kojima M, Matsuo H, Eto T. Cloning and characterization of cDNA encoding a precursor for human adrenomedullin. Biochem Biophys Res Commun. 1993;194:720-725.[Medline]
  3. Sakata J, Shimobuko T, Kitamura K, et al. Molecular cloning and biological activities of rat adrenomedullin, a hypotensive peptide. Biochem Biophys Res Commun. 1993;195:921-927.[Medline]
  4. Eguchi S, Hirata Y, Iwasaki H, et al. Structure-activity relationship of adrenomedullin, a novel vasodilatory peptide, in cultured rat vascular smooth muscle cells. Endocrinology. 1994;135:2454-2458.[Abstract]
  5. Entzeroth M, Doods HN, Wieland HA, Wienen W. Adrenomedullin mediates vasodilation via CGRP1 receptors. Life Sci. 1995;56:PL19-PL25.[Medline]
  6. Eguchi S, Hirata Y, Kano H, et al. Specific receptors for adrenomedullin in cultured rat vascular smooth muscle cells. FEBS Lett. 1994;340:226-230.[Medline]
  7. Kapas S, Catt K, Clark A. Cloning and expression of cDNA encoding a rat adrenomedullin receptor. J Biol Chem. 1995;270:25344-25347.[Abstract/Free Full Text]
  8. McLatchie LM, Fraser NJ, Main MJ, et al. RAMPs regulate the transport and ligand specificity of the calcitonin-receptor-like receptor. Nature. 1998;393:333-339.[Medline]
  9. Poyner DR, Sexton PM, Marshall I, et al. International union of pharmacology. XXXII. The mammalian calcitonin gene-related peptides, adrenomedullin, amylin, and calcitonin receptors. Pharmacol Rev. 2002;54:233-246.[Abstract/Free Full Text]
  10. Muff R, Born W, Fischer JA. Adrenomedullin selectivity of calcitonin-like receptor/receptor activity modifying proteins. Hypertens Res. 2003;26:S3-S8.[Medline]
  11. Prado MA, Evans-Bain B, Oliver KR, Dickerson IM. The role of the CGRP-receptor component protein (RCP) in adrenomedullin receptor signal transduction. Peptides. 2001;22:1773-1781.[Medline]
  12. Hwang ISS, Tang F. The distribution and gene expression of adrenomedullin in the rat brain: peptide/mRNA and precursor/active peptide relationships. Neurosci Lett. 1999;267:85-88.[Medline]
  13. Hwang ISS, Tang F. Peripheral distribution and gene expression of adrenomedullin in the rat: possible source of blood adrenomedullin. Neuropeptides. 2000;34:32-37.[Medline]
  14. Ichiki Y, Kitamura K, Kangawa K, Kawamoto M, Matsuo H, Eto T. Distribution and characterization of immunoreactive adrenomedullin in human tissue and plasma. FEBS Lett. 1994;338:6-10.[Medline]
  15. Sakata J, Shimokubo T, Kitamura K, et al. Distribution and characterization of immunoreactive rat adrenomedullin in tissue and plasma. FEBS Lett. 1994;352:105-108.[Medline]
  16. Cameron VA, Fleming AM. Novel sites of adrenomedullin gene expression in mouse and rat tissues. Endocrinology. 1998;139:2253-2264.[Abstract/Free Full Text]
  17. Abe K, Minegishi T, Ibuki Y, Kojima M, Kangawa K. Expression of adrenomedullin in the human corpus luteum. Fertil Steril. 2000;74:141-145.[Medline]
  18. Upton PD, Austin C, Taylor GM, et al. Expression of adrenomedullin and its binding sites in the rat uterus: increased number of binding sites and AM messenger ribonucleic acids in 20-day pregnant rats compared with non-pregnant rats. Endocrinology. 1997;138:2508-2513.[Abstract/Free Full Text]
  19. Li YY, Hwang IS, O WS, Tang F. Adrenomedullin peptide: gene expression of adrenomedullin, its receptors and receptor activity modifying proteins, and receptor binding in rat testis–actions on testosterone secretion. Biol Reprod. 2006;75:183-188.[Abstract/Free Full Text]
  20. Pewitt EB, Haleem R, Wang Z. Adrenomedullin gene is abundantly expressed and directly regulated by androgen in the rat ventral prostate. Endocrinology. 1999;140:2382-2386.[Abstract/Free Full Text]
  21. Jimenez N, Calvo A, Martinez A, Rosell D, Cuttitta F, Montuenga LM. Expression of adrenomedullin and proadrenomedullin N-terminal 20 peptide in human and rat prostate. J Histochem Cytochem. 1999;47:1167-1177.[Abstract/Free Full Text]
  22. Hwang IS, Autelitano DJ, Wong PY, Leung GP, Tang F. Co-expression of adrenomedullin and adrenomedullin receptors in rat epididymis: distinct physiological actions on anion transport. Biol Reprod. 2003;68:2005-2012.[Abstract/Free Full Text]
  23. Plas E, Berger P, Hermann M, Pflüger H. Effects of aging on male fertility? Exp Gerontol. 2000;35:543-551.[Medline]
  24. Hermann M, Untergasser G, Rumpold H, Berger P. Aging of the male reproductive system. Exp Gerontol. 2000;35:1267-1279.[Medline]
  25. Santiemma V, Rossi F, Guerrini L, et al. Adrenomedullin inhibits the contraction of cultured rat testicular peritubular myoid cells induced by endothelin-1. Biol Reprod. 2001;64:619-624.[Abstract/Free Full Text]
  26. Marinoni E, Di Iorio R, Villaccio B, et al. Adrenomedullin in human male reproductive system. Eur J Obstet Gynecol Reprod Biol. 2005;122:195-198.[Medline]
  27. Mendis-Handagama SM, Gelber SJ. Signs of aging are apparent in the testis interstitium of Sprague Dawley rats at 6 months of age. Tissue Cell. 1995;27:689-699.[Medline]
  28. Wang C, Sinha Hikim AP, Lue YH, Leung A, Baravarian S, Swerdloff RS. Reproductive aging in the Brown Norway rat is characterized by accelerated germ cell apoptosis and is not altered by luteinizing hormone replacement. J Androl. 1999;20:509-518.[Abstract/Free Full Text]
  29. Sartin JL, Lamperti AA. FSH and LH response to testosterone and gonadotropin-releasing hormone in aging male rats. Exp Aging Res. 1984;10:183-187.[Medline]
  30. Ventura S, Lau WA, Buljubasich S, Pennefather JN. Calcitonin gene-related peptide (CGRP) inhibits contractions of the prostatic stroma of the rat but not the guinea-pig. Regul Pept. 2000;91:63-73.[Medline]
  31. Shibata Y, Kashiwagi B, Arai S, Magari T, Suzuki K, Honma S. Participation of adrenomedullin and its relation with vascular endothelial growth factor in androgen regulation of prostatic blood flow in vivo. Urology. 2006;68:1127-1131.[Medline]
  32. Mungan NA, Mungan G, Basar MM, Baykam M, Atan A. Effect of seminal plasma calcitonin levels on sperm motility. Arch Androl. 2001;47:113-117.[Medline]
  33. Foresta C, Caretto A, Indino M, Betterle C, Scandellari C. Calcitonin in human seminal plasma and its localization on human spermatozoa. Andrologia. 1986;18:470-473.[Medline]
  34. Silvestroni L, Menditto A, Frajese G, Gnessi L. Identification of calcitonin receptors in human spermatozoa. J Clin Endocrinol Metab. 1987;65:742-746.[Abstract/Free Full Text]



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