| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Departments of Cell Biology, Physiology, and Immunology (F.G., M.L.B., L.P., E.A., M.T.-S.), and Pathology (C.M.), University of Córdoba, 14004 Córdoba, Spain; Centre for Molecular Biotechnology (L.K.C., A.C.H.), Queensland University of Technology, Brisbane Q4001, Queensland, Australia; and Departments of Medicine (F.F.C.) and Physiology (C.D.), University of Santiago de Compostela, 15705 Santiago de Compostela, Spain
Address all correspondence and requests for reprints to: Manuel Tena-Sempere, M.D., Physiology Section. Department of Cell Biology, Physiology, and Immunology, Faculty of Medicine, University of Córdoba, Avda. Menéndez Pidal s/n, 14004 Córdoba, Spain. E-mail: fi1tesem{at}uco.es.
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The physiological relevance of the GHS-signaling system has been recently substantiated by the identification of its endogenous ligand, ghrelin. Ghrelin is a 28-amino acid peptide with an essential n-octanoyl modification at Ser3 that is primarily expressed in stomach and hypothalamus (1, 2). As expected for the endogenous counterpart of GHSs, this molecule has been proven to elicit GH secretion in vivo and from anterior pituitary cells in vitro (1, 2, 8, 9, 10). In addition, ghrelin is able to induce food intake and adiposity in rodents (9, 11, 12), and its involvement in the long-term control of body weight in humans has been recently proposed (13). Notably, the above biological effects of ghrelin are mainly carried out at central neuroendocrine levels, i.e. the hypothalamus and/or pituitary. However, additional as-yet-undefined peripheral actions of ghrelin are likely to take place. In this context, a widespread pattern of expression of the genes encoding ghrelin and its cognate receptor has been reported very recently in humans (14), and GHS/ghrelin-binding sites have been demonstrated in a variety of peripheral human tissues (15). In addition, a number of noncentral tissues, such as placenta and kidney, have been shown to express ghrelin protein (16, 17). However, the physiological role of ghrelin signaling in such peripheral systems remains to be determined.
Among the novel biological actions of ghrelin, a role for this molecule in the direct control of male gonadal function has been recently suggested in rodents. Our group has provided evidence for the expression of ghrelin and its cognate receptor in rat testis (18, 19). In addition, a specific ghrelin gene-derived transcript has been recently identified in mouse testis (20). However, evaluation of expression or direct biological actions of ghrelin in gonads from nonrodent species, including humans, has not been conducted. Moreover, the presence of ghrelin and its signaling system in the ovary remains largely unexplored, although expression of ghrelin mRNA in human ovarian tissue has been preliminarily reported very recently (14). In this sense, the ovary is a complex organ in which different endocrine and locally produced steroidal and nonsteroidal regulators cooperate to ensure complete ovarian function (21, 22, 23). In the present study, assessment of expression and cellular location of ghrelin and its functional receptor, i.e. the type 1a GHS-R, was conducted in the cyclic human ovary by immunohistochemical labeling using specific polyclonal antibodies. Overall, novel evidence for the expression of both components (ligand and receptor) of ghrelin signaling system within the human ovary paves the way for further studies on the role of this recently cloned molecule in ovarian physiology and pathophysiology.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Human ovaries were obtained from the files of the Department of Pathology of the University of Cordoba, on approval of the local Ethical Committee. In detail, from a larger series, 25 ovaries corresponding to hysterectomized and bilaterally salpingo-oophorectomized women caused by uterine lesions were selected. Patients did not show ovarian pathology, nor were they undergoing hormonal treatment. In addition, they presented with normal menstrual cycles. Normal cyclicity was confirmed by the presence of a corpus luteum (CL) of the current cycle (during the luteal phase) and of a regressing CL of the preceding cycle (during the follicular phase). The day of the cycle was assigned by considering the menstrual history and dating of the endometrium (24) and CL (25). The standard cycle was considered to be 28 d and was divided into follicular (from d 1 to d 14) and early (d 15–19), mid (d 20–24), and late (d 25–27) luteal phases. At least five ovaries per phase were studied.
Healthy ovarian follicles were classified using previously published criteria (26). To simplify the results, follicles were divided into four groups: 1) resting follicles, corresponding to nongrowing follicles and including primordial, intermediary, and primary follicles; 2) secondary preantral follicles (class 1); 3) early antral follicles (classes 2 and 3), and 4) antral follicles, from class 4 onward. In addition, atretic follicles were considered as early (stages A and B) or advanced (stages C and D), as described in detail elsewhere (26). Finally, CL were classified as young (d 15–19), mature (d 20–24), old (d 25–27), and regressing (during the follicular phase of the following cycle) CL.
Polyclonal antighrelin and anti-GHS-R1a antibodies
For analysis of ghrelin peptide expression, a rabbit antighrelin polyclonal antiserum, kindly provided by Drs. M. Kojima and K. Kangawa (Department of Biochemistry, National Cardiovascular Center Research Institute, Osaka, Japan), was used as primary antibody. This antibody was generated as described in detail elsewhere (27), using [Cys0]-rat ghrelin (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28) as antigen, and it is able to recognize both rat and human ghrelin (28). High specificity of this antiserum is demonstrated by absence of significant cross-reactivity with other peptides, as reported earlier (28). In addition, immunohistochemical labeling of GHS-R1a protein was conducted using a rabbit polyclonal antibody generated against a synthetic peptide corresponding to the C-terminal fragment (RAWTESSINTC) of the human GHS-R1a protein conjugated to diptheria toxin (Mimotopes, Melbourne, Australia), as described in detail previously (29). Western analyses using this antibody demonstrated a single specific band of approximately the predicted size (45 kDa) for the GHS-R1a in the ALVA-41 and DU145 prostate cancer cell lines (Chopin, L. K., and A. C. Herington, personal observation), which have been proven to express the GHS-R1a mRNA isoform and GHS-R1a protein (29).
Immunohistochemistry
Immunohistochemistry was performed on routinely neutral-buffered formaldehyde-fixed, paraffin-embedded tissues. In detail, ovarian sections (5 µm thick) were placed on poly-L-lysine-coated slides and, after dewaxing in xylene and rehydration in ethanol, the samples were incubated in 2% hydrogen peroxide in methanol for 30 min to quench endogenous peroxidase followed by washing in PBS. Specifically, sections for GHS-R1a immunolabeling were immersed in 10 mM citrate buffer and submitted to antigen retrieval in a microwave oven (2 x 5 min at 700 W). As general immunohistochemical procedure, sections were allowed to cool at room temperature, washed in PBS, blocked with normal serum, and incubated overnight with the primary antibody: antighrelin (diluted 1:400); anti-GHS-R1a (diluted 1:200). The sections were then processed according to the avidin-biotin-peroxidase complex technique following previously described methods (30, 31). Negative controls were run routinely in parallel by replacing the primary antibody by preimmune serum or PBS. In addition, positive controls for ghrelin and GHS-R1a immunostaining, were included. Thus, reactions in rat testicular samples (18, 19) and human pituitary sections (Peterborough Hospital NHS Tissue Bank, Peterborough, UK) were conducted using antighrelin and anti-GHS-R1a primary antibodies, respectively, yielding strong immunoreactivity. As an additional control for the specificity of GHS-R1a antibody, immunohistochemical reactions using human pituitary and ovarian tissue were carried out following preabsorption of the antiserum overnight at 4 C with 1 mg/ml of the synthetic peptide (RAWTESSINTC) to which it was raised against. This procedure completely abolished immunolabeling of pituitary and ovarian sections (Fig. 1
).
|
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Evaluation of the presence and pattern of cellular expression of ghrelin protein in the cyclic human ovary was conducted by immunohistochemistry using a specific antighrelin polyclonal antibody (27, 28). Our analysis demonstrated that hilus interstitial cells, found at the ovarian hilus as clumps of large epithelioid cells (Fig. 2A), showed strong ghrelin immunostaining (Fig. 2B). In positive cells, the cytoplasm was uniformly stained, whereas cell nuclei were negative. As a control for specificity of detection, omission of primary antighrelin antibody and its substitution either by PBS (data not shown) or preimmune serum (Fig. 2A) resulted in negative staining of hilus cells. Otherwise, secondary interstitial cells derived from the theca interna of atretic follicles failed to show specific ghrelin immunostaining.
|
), from d 16 of the cycle onward as well as in mature CL (Fig. 2D). Specific ghrelin immunostaining was observed in the cytoplasm of granulosa-lutein cells (GLC) (Fig. 2E) and was stronger in the inner aspect of the granulosa-lutein layer (GLL). Theca-lutein cells were negative. Finally, ghrelin immunoreactivity was present in scarce, isolated GLC from old CL, whereas it was absent in regressing CL. GHS-R expression in cyclic human ovary
A similar immunohistochemical procedure was used for assessment of the presence and pattern of cellular expression of GHS-R1a peptide in the cyclic human ovary, using a specific anti-GHS-R1a polyclonal antibody (29). In contrast to ghrelin, GHS-R1a protein expression showed a wider pattern of tissue distribution within the human ovary. Concerning the follicular compartment, oocytes showed cytoplasmic immunostaining that was stronger in small follicles (Fig. 3, A–C) and fainter in larger ones. In addition, GHS-R1a protein was detected in somatic follicular cells, with an expression profile that was roughly parallel to follicle development. Overall, resting follicles showed variable GHS-R1a immunoreactivity. In detail, (pre)granulosa cells in primordial follicles were not immunostained (Fig. 3A), whereas cuboidal granulosa cells from intermediary (Fig. 3B) and primary (Fig. 3C) follicles presented negligible to faint GHS-R1a signal. In contrast, in secondary preantral follicles, clear-cut GHS-R1a immunoreactivity was detected in the cytoplasm of granulosa cells (Fig. 3D). In early antral follicles (classes 2 and 3), immunostaining was weak in granulosa cells and stronger in theca cells (Fig. 3E). From this stage of follicular development onward, healthy antral follicles showed intense GHS-R1a immunoreactivity in both granulosa and theca layers (Fig. 3, F–H).
|
, A and B), whereas intensity of GHS-R1a immunoreactivity remained constant in theca cells (Fig. 4B). At advanced stages of atresia, secondary interstitial cells derived from the theca interna showed strong GHS-R1a immunostaining (Fig. 4C). Similarly, immunoreactivity for GHS-R1a peptide was also observed in hilus interstitial cells (Fig. 4, D and E).
|
), mature (Fig. 5B), old (Fig. 5C), and regressing (Fig. 5D) CL. It is worth noting that cells in the CL immunolabeled with anti-GHS-R1a antibody corresponded to steroidogenic luteal cells, recognizable by their round nuclei and large cytoplasm.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Using RT-PCR, expression of ghrelin gene in human ovary has been postulated very recently (14). Present data further substantiate this preliminary observation and demonstrate for the first time the actual presence of the peptide in the human female gonad. Notably, immunolocalization of ghrelin within human ovarian tissue revealed a compartmentalized distribution of the protein, with strong signals being detected in hilus interstitial cells. It is worth noting that this cell type shows distinctive morphological characteristics, such as the presence of crystals of Reinke, that are identical to those of differentiated testicular Leydig cells (33). In fact, our molecular and immunohistochemical analyses indicated that testicular expression of ghrelin is restricted to mature Leydig cells, both in rats (18, 19) and humans (Gaytan, F., and M. Tena-Sempere, manuscript in preparation). Thus, ghrelin expression may be an additional feature shared by ovarian hilus and testicular Leydig cells. Indeed, relaxin-like factor, another useful marker of testicular Leydig cell differentiation (34, 35), is expressed also in human ovarian hilus cells (36). Interestingly, Leydig cell-specific expression of ghrelin in rat testis is under regulation of pituitary LH (19), and a role for ghrelin as direct modulator of LH-driven testicular testosterone secretion has been recently reported (18). Hilus interstitial cells are steroidogenically active, with ability to secrete testosterone in response to LH stimulation (33). Whether ghrelin may have a direct role in the regulation of androgen secretion by hilus cells remains to be evaluated, although the presence of its cognate receptor, the GHS-R1a, in the very same cell type (Fig. 4) is compatible with this hypothesis. Presumably, the contribution of hilus cells to the pool of circulating androgens in women is not fully established (37). Yet hilus cells can undergo hyperplasia, which is frequently observed after menopause and may be associated with endocrine disturbances. In addition, rare cases of virilizing tumors of hilus cells have been described in postmenopausal women (38). Overall, our present data pave the way for analysis of the role, if any, of ghrelin signaling in the physiological and pathophysiological control of hilus cell steroidogenic function.
In contrast to hilus cells, other interstitial androgen-producing cells in the ovary, such as secondary interstitial cells derived from atretic follicles, showed an absence of ghrelin immunoreactivity. The reason for such a divergence is unclear but as for testicular Leydig cells, ghrelin may serve as selective marker for highly differentiated, androgen-secreting (i.e. hilus) cells within the ovary. Yet the presence of minute amounts of ghrelin peptide in other ovarian androgen-producing cells, at levels below the sensitivity threshold of our immunohistochemical assays, cannot be completely ruled out. Conversely, ghrelin protein was clearly detected in luteal cells in a defined period following CL formation that corresponded to young and mature luteal tissue. Of note, such a profile of ghrelin expression in the CL is roughly coincident with its peak in functional activity within the ovarian cycle. Thus, maximum secretion of progesterone by CL cells, between d 17 and d 23 of the cycle (39), grossly corresponded to the period when strong ghrelin immunostaining was detected in the cytoplasm of granulosa-lutein cells. Moreover, the presence of GHS-R1a peptide in both GLCs and theca-lutein cells during the same time frame suggests a potential regulatory role of locally produced ghrelin in the control of CL function. Notably, the pattern of expression of ghrelin in the human ovary is similar to that observed by our group in the cyclic rat ovary, in which ghrelin immunoreactivity was mainly located in steroidogenic luteal cells (Caminos, J. E., M. Tena-Sempere, and C. Dieguez, submitted for publication). Moreover, expression of ghrelin has been recently demonstrated in additional steroidogenic tissues, such as the placenta (16) and testis (18, 19), and we have provided evidence for a direct modulatory action of ghrelin on stimulated testosterone secretion (18). In this context, elucidation of ghrelin effects on CL steroidogenic function merits further investigation.
Immunohistochemical analyses of the presence and cellular location of GHS-R1a protein within the cyclic ovary indicated a somewhat wider pattern of distribution than that of ghrelin, with detectable specific signals in oocytes as well as somatic follicular cells; luteal cells from young, mature, old, and regressing CL; and interstitial hilus cells. To date an extremely limited number of studies have addressed the expression of the cognate ghrelin receptor, namely the GHS-R, in rodent and human gonads, and partially conflicting results have been reported. Expression of the GHS-R gene in rat testis has been demonstrated (18), but no conclusive data on GHS-R expression in rodent ovary have been published. Notably, our recent analyses indicated strong expression of the mRNA encoding the functionally active form of GHS-R, i.e. the 1a GHS-R subtype, in rat testis during the adult period (Barreiro, M. L., and M. Tena-Sempere, submitted for publication). In keeping with data from rodent testis, high levels of GHS/ghrelin binding were demonstrated in human testis (15). Similarly, ghrelin-binding sites were also identified in the human ovary, thus suggesting the presence of functional receptor (15). These results are in good agreement with our present immunohistochemical results.
In contrast, however, in a very recent report, systematic screening of GHS-R1a mRNA expression in a wide array of human tissues, using real-time RT-PCR, failed to detect this transcript in the human ovary (14). Conversely, positive amplification of the mRNA encoding the truncated GHS-R1b form was observed (14). The reasons for the above discrepancies remain obscure because no detailed description of the endocrine background of the assayed ovarian samples are offered in the mentioned study (14). In this sense, the ovary undergoes striking changes during development and within the cycle, making it possible that net expression levels of a target gene may vary dramatically. Additionally, changes in the balance between 1a and 1b forms of GHS-R expression may take place in the human ovary under certain conditions. This seems to be the case for rat testis in which changes in the pattern of alternative splicing of GHS-R gene are observed throughout postnatal development. Thus, whereas strong expression of GHS-R1a mRNA is detected from puberty onward, in earlier stages of testicular development the predominant receptor form is likely the truncated GHS-R1b type (Barreiro, M. L., and M. Tena-Sempere, submitted for publication). Whether a similar phenomenon operates in the ovary is yet to be proven. In this context, additional analyses on the expression of the mRNA encoding the GHS-R type 1a as well as that of its cognate ligand, ghrelin, in human ovarian tissue would help to further delineate the pattern of expression and regulation of this signaling system in the female gonad. Nevertheless, data from binding studies (15) and immunohistochemical labeling (present results) strongly suggest that functional (i.e. type 1a) GHS-Rs are expressed in the cyclic human ovary.
Our immunohistochemical analyses demonstrated that expression of GHS-R1a peptide in somatic cells from ovarian follicles roughly paralleled follicular development, suggesting a potential relationship between GHS-R expression and follicle growth. Thus, although weak to negligible staining was observed in resting follicles, GHS-R1a protein expression in granulosa cells was first consistently observed in early growing follicles (secondary preantral follicles), and stronger GHS-R1a immunoreactivity became detectable in the granulosa and theca layers of growing follicles, from class 4 onward. Regulation of follicular growth is an incompletely understood phenomenon, in which, in addition to pituitary gonadotropins, a plethora of systemic and locally produced steroid and nonsteroid factors cooperate to ensure proper follicle development and ovarian function (21, 22, 23, 26, 39, 40). The involvement of ghrelin in such a regulatory network remains to be determined. Of interest, a role for ghrelin, acting through its type 1a receptor, as a modulator of cell proliferation and tumor growth, has been recently proposed (29), making it worthy to evaluate the potential implication of this novel signal in follicle development. Overall, our current immunohistochemical data on the simultaneous expression of ghrelin and its cognate receptor in several ovarian compartments are compatible with a potential action of locally produced ghrelin in the auto/paracrine regulation of human ovarian function. Additionally, the wide pattern of ovarian GHS-R1a expression makes it possible that circulating ghrelin may operate on specific cell targets within the human cyclic ovary. In this sense, ghrelin has recently emerged as a pivotal factor in food intake control and energy homeostasis (11, 12, 13), and direct gonadal actions have been demonstrated for other peripheral signals with such key actions in the regulation of body weight and energy expenditure, as the adipocyte-derived plasma hormone, leptin (41). Indeed, leptin has been proven to operate directly at the ovarian level to modulate follicular steroidogenesis and ovulation (42, 43, 44). The role, if any, of systemic ghrelin in the control of ovarian function remains to be elucidated.
In conclusion, our immunohistochemical analyses provide compelling evidence for the presence of ghrelin and its cognate functional receptor, namely the type 1a GHS-R, in the cyclic human ovary with distinct but partially overlapping patterns of cellular distribution. The expression of both components (ligand and receptor) of ghrelin signaling system within the human ovary underscores a potential regulatory action of this novel molecule in the direct control of ovarian function.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
Abbreviations: CL, Corpora lutea; GHS, GH secretagogue; GHS-R, GHS receptor; GLC, granulosa-lutein cell; GLL, granulosa-lutein layer.
Received July 30, 2002.
Accepted October 30, 2002.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
 |
|
 |
|
  C. I. Messini, K. Dafopoulos, N. Chalvatzas, P. Georgoulias, and I. E. Messinis Effect of ghrelin on gonadotrophin secretion in women during the menstrual cycle Hum. Reprod., April 1, 2009; 24(4): 976 - 981. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Gronberg, A. V. Tsolakis, L. Magnusson, E. T. Janson, and J. Saras Distribution of Obestatin and Ghrelin in Human Tissues: Immunoreactive Cells in the Gastrointestinal Tract, Pancreas, and Mammary Glands J. Histochem. Cytochem., September 1, 2008; 56(9): 793 - 801. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C Letelier, F Mallo, T Encinas, J M Ros, and A Gonzalez-Bulnes Glucogenic supply increases ovulation rate by modifying follicle recruitment and subsequent development of preovulatory follicles without effects on ghrelin secretion Reproduction, July 1, 2008; 136(1): 65 - 72. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. E. Caminos, R. Nogueiras, F. Gaytan, R. Pineda, C. R. Gonzalez, M. L. Barreiro, J. P. Castano, M. M. Malagon, L. Pinilla, J. Toppari, et al. Novel Expression and Direct Effects of Adiponectin in the Rat Testis Endocrinology, July 1, 2008; 149(7): 3390 - 3402. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Viani, A. Vottero, F. Tassi, G. Cremonini, C. Sartori, S. Bernasconi, B. Ferrari, and L. Ghizzoni Ghrelin Inhibits Steroid Biosynthesis by Cultured Granulosa-Lutein Cells J. Clin. Endocrinol. Metab., April 1, 2008; 93(4): 1476 - 1481. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. J. Moran, M. Noakes, P. M. Clifton, and R. J. Norman The Use of Anti-Mullerian Hormone in Predicting Menstrual Response after Weight Loss in Overweight Women with Polycystic Ovary Syndrome J. Clin. Endocrinol. Metab., October 1, 2007; 92(10): 3796 - 3802. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. M. Raso, G. Bianco, A. Iacono, E. Esposito, G. Autore, M. C. Ferrante, A. Calignano, and R. Meli Maternal adaptations to pregnancy in spontaneously hypertensive rats: leptin and ghrelin evaluation J. Endocrinol., September 1, 2007; 194(3): 611 - 619. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Tropea, F. Tiberi, F. Minici, M. Orlando, M. F. Gangale, F. Romani, F. Miceli, S. Catino, S. Mancuso, M. Sanguinetti, et al. Ghrelin Affects the Release of Luteolytic and Luteotropic Factors in Human Luteal Cells J. Clin. Endocrinol. Metab., August 1, 2007; 92(8): 3239 - 3245. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Kluge, P. Schussler, M. Uhr, A. Yassouridis, and A. Steiger Ghrelin Suppresses Secretion of Luteinizing Hormone in Humans J. Clin. Endocrinol. Metab., August 1, 2007; 92(8): 3202 - 3205. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Fernandez-Fernandez, M. Tena-Sempere, J. Roa, J. M. Castellano, V. M Navarro, E. Aguilar, and L. Pinilla Direct stimulatory effect of ghrelin on pituitary release of LH through a nitric oxide-dependent mechanism that is modulated by estrogen Reproduction, June 1, 2007; 133(6): 1223 - 1232. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. C Garcia, M. Lopez, C. V Alvarez, F. Casanueva, M. Tena-Sempere, and C. Dieguez Role of ghrelin in reproduction Reproduction, March 1, 2007; 133(3): 531 - 540. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Ishikawa, H. Fujioka, T. Ishimura, A. Takenaka, and M. Fujisawa Ghrelin Expression in Human Testis and Serum Testosterone Level J Androl, March 1, 2007; 28(2): 320 - 324. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A Majuri, M Santaniemi, K Rautio, A Kunnari, J Vartiainen, A Ruokonen, Y A Kesaniemi, J S Tapanainen, O Ukkola, and L Morin-Papunen Rosiglitazone treatment increases plasma levels of adiponectin and decreases levels of resistin in overweight women with PCOS: a randomized placebo-controlled study Eur. J. Endocrinol., February 1, 2007; 156(2): 263 - 269. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C.-M. Yeung, C.-B. Chan, N. Y S Woo, and C. H K Cheng Seabream ghrelin: cDNA cloning, genomic organization and promoter studies. J. Endocrinol., May 1, 2006; 189(2): 365 - 379. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Panidis, D. Farmakiotis, G. Koliakos, D. Rousso, A. Kourtis, I. Katsikis, C. Asteriadis, V. Karayannis, and E. Diamanti-Kandarakis Comparative study of plasma ghrelin levels in women with polycystic ovary syndrome, in hyperandrogenic women and in normal controls Hum. Reprod., August 1, 2005; 20(8): 2127 - 2132. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Kellokoski, S. M. Poykko, A. H. Karjalainen, O. Ukkola, J. Heikkinen, Y. A. Kesaniemi, and S. Horkko Estrogen Replacement Therapy Increases Plasma Ghrelin Levels J. Clin. Endocrinol. Metab., May 1, 2005; 90(5): 2954 - 2963. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Gaytan, C. Morales, M. L. Barreiro, P. Jeffery, L. K. Chopin, A. C. Herington, F. F. Casanueva, E. Aguilar, C. Dieguez, and M. Tena-Sempere Expression of Growth Hormone Secretagogue Receptor Type 1a, the Functional Ghrelin Receptor, in Human Ovarian Surface Epithelium, Mullerian Duct Derivatives, and Ovarian Tumors J. Clin. Endocrinol. Metab., March 1, 2005; 90(3): 1798 - 1804. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. R. Kumar Divide and Differentiate: Ghrelin Instructs the Leydig Cells Endocrinology, November 1, 2004; 145(11): 4822 - 4824. [Full Text] [PDF]
|
|
|
|
 |
|
 G. Rindi, A. Torsello, V. Locatelli, and E. Solcia Ghrelin Expression and Actions: A Novel Peptide for an Old Cell Type of the Diffuse Endocrine System Experimental Biology and Medicine, November 1, 2004; 229(10): 1007 - 1016. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. J. Moran, M. Noakes, P. M. Clifton, G. A. Wittert, L. Tomlinson, C. Galletly, N. D. Luscombe, and R. J. Norman Ghrelin and Measures of Satiety Are Altered in Polycystic Ovary Syndrome But Not Differentially Affected by Diet Composition J. Clin. Endocrinol. Metab., July 1, 2004; 89(7): 3337 - 3344. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Nogueiras, M. L. Barreiro, J. E. Caminos, F. Gaytan, J. S. Suominen, V. M. Navarro, F. F. Casanueva, E. Aguilar, J. Toppari, C. Dieguez, et al. Novel expression of resistin in rat testis: functional role and regulation by nutritional status and hormonal factors J. Cell Sci., July 1, 2004; 117(15): 3247 - 3257. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. J. van der Lely, M. Tschop, M. L. Heiman, and E. Ghigo Biological, Physiological, Pathophysiological, and Pharmacological Aspects of Ghrelin Endocr. Rev., June 1, 2004; 25(3): 426 - 457. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Gaytan, M. L. Barreiro, J. E. Caminos, L. K. Chopin, A. C. Herington, C. Morales, L. Pinilla, R. Paniagua, M. Nistal, F. F. Casanueva, et al. Expression of Ghrelin and Its Functional Receptor, the Type 1a Growth Hormone Secretagogue Receptor, in Normal Human Testis and Testicular Tumors J. Clin. Endocrinol. Metab., January 1, 2004; 89(1): 400 - 409. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. M. Malagon, R. M. Luque, E. Ruiz-Guerrero, F. Rodriguez-Pacheco, S. Garcia-Navarro, F. F. Casanueva, F. Gracia-Navarro, and J. P. Castano Intracellular Signaling Mechanisms Mediating Ghrelin-Stimulated Growth Hormone Release in Somatotropes Endocrinology, December 1, 2003; 144(12): 5372 - 5380. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E. Caminos, R. Nogueiras, M. Blanco, L. M. Seoane, S. Bravo, C. V. Alvarez, T. Garcia-Caballero, F. F. Casanueva, and C. Dieguez Cellular Distribution and Regulation of Ghrelin Messenger Ribonucleic Acid in the Rat Pituitary Gland Endocrinology, November 1, 2003; 144(11): 5089 - 5097. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
U. Pagotto, A. Gambineri, C. Pelusi, S. Genghini, M. Cacciari, B. Otto, T. Castaneda, M. Tschop, and R. Pasquali Testosterone Replacement Therapy Restores Normal Ghrelin in Hypogonadal Men J. Clin. Endocrinol. Metab., September 1, 2003; 88(9): 4139 - 4143. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
