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Adrenomedullin Peptide: Gene Expression of Adrenomedullin, its Receptors and Receptor Activity Modifying Proteins, and Receptor Binding in Rat Testis—Actions on Testosterone Secretion¹

Departments of Physiology³ Anatomy,⁴ Centre of Reproduction, Development, and Growth,⁵ and Centre of Heart, Brain, Hormone, and Healthy Aging,⁶ Faculty of Medicine, The University of Hong Kong, Hong Kong

ABSTRACT

Adrenomedullin (ADM) has been shown to be present in the human and rat male reproductive systems. This study demonstrates the expression of ADM in the rat testis and its effect on the secretion of testosterone. Whole testicular extracts had 5.43 ± 0.42 fmol of immunoreactive ADM per milligram of protein and 84 ± 8 fg of ADM mRNA per picogram of Actb (ß-actin) mRNA. Immunocytochemical studies showed positive ADM immunostaining in the Leydig cells and in the Sertoli cells. Gel filtration chromatography of testicular extracts showed two peaks, with the predominant one eluting at the position of the ADM precursor. Furthermore, the testis was shown to coexpress mRNAs encoding the calcitonin receptor-like receptor and receptor activity modifying protein 1 (Ramp1), Ramp2, and Ramp3. These account for the specific binding of ADM to the testis, which was partially inhibited by human ADM (22–52) and by human calcitonin gene-related peptide (8–37), the ADM and calcitonin gene-related peptide receptor antagonists, respectively. Administration of ADM to testicular blocks in vitro resulted in a dose-dependent inhibition of hCG-stimulated release of testosterone, which was abolished by the administration of ADM (22–52). Our results suggest a paracrine effect of ADM on testicular steroidogenesis.

aging, human chorionic gonadotropin, testis, testosterone

¹ Supported by grant HKU 7451/04M from the Research Grants Council of Hong Kong.

² Correspondence: Fai Tang, Department of Physiology and Centre of Heart, Brain, Hormone and Healthy Aging, Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong. FAX: 852 2 855 9730; ftang{at}hkucc.hku.hk

This article has been cited by other articles:

				Y.-Y. Li, L. Li, I. S.-S. Hwang, F. Tang, and W.-S. O Coexpression of Adrenomedullin and Its Receptors in the Reproductive System of the Rat: Effects on Steroid Secretion in Rat Ovary Biol Reprod, August 1, 2008; 79(2): 200 - 208. [Abstract] [Full Text] [PDF]

				Y.-F. Chan, F. Tang, and W.-S. O Adrenomedullin in the Rat Testis. II: Its Production, Actions on Inhibin Secretion, Regulation by Follicle-Stimulating Hormone, and Its Interaction with Endothelin 1 in the Sertoli Cell Biol Reprod, April 1, 2008; 78(4): 780 - 785. [Abstract] [Full Text] [PDF]

				Y.-F. Chan, W.-S. O, and F. Tang Adrenomedullin in the Rat Testis. I: Its Production, Actions on Testosterone Secretion, Regulation by Human Chorionic Gonadotropin, and Its Interaction with Endothelin 1 in the Leydig Cell Biol Reprod, April 1, 2008; 78(4): 773 - 779. [Abstract] [Full Text] [PDF]

				Y.-Y. Li, W.-S. O, and F. Tang Effect of Aging on the Expression of Adrenomedullin and Its Receptor Component Proteins in the Male Reproductive System of the Rat J. Gerontol. A Biol. Sci. Med. Sci., December 1, 2007; 62(12): 1346 - 1351. [Abstract] [Full Text] [PDF]