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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 Cell¹

Departments of Anatomy³ and Physiology,⁴ the Centre of Heart, Brain, Hormone, and Healthy Aging,⁵ and the Centre of Reproduction, Development, and Growth,⁶ Faculty of Medicine, The University of Hong Kong, Hong Kong, China

ABSTRACT

Based on the finding of gene expression of adrenomedullin (Adm) and its receptor components in the rat testis, a paracrine effect of ADM on testicular steroidogenesis has been suggested by our group. The present study demonstrates the gene expression of Adm and the effect of ADM on testosterone production in the Leydig cell. The regulation of ADM by hCG and its interaction with endothelin 1 (EDN1) in the rat Leydig cells are also observed. Primary culture of Leydig cells produced Adm mRNA and secreted 275 ± 19 pg immunoreactive ADM per 10⁶ cells in 24 h. In addition, the Leydig cell was shown to coexpress mRNAs encoding for the calcitonin receptor-like receptor (CALCRL) and receptor activity-modifying protein (RAMP1, RAMP2, and RAMP3). These may account for the specific binding of ADM to the Leydig cells. Administration of ADM to Leydig cells resulted in an inhibition of hCG- and EDN1-stimulated testosterone production. Correlated with this, ADM reduced EDN1 production, whereas its production was increased by EDN1. Furthermore, the production of ADM and the mRNA levels of Calcrl and Ramp2 were suppressed by hCG. Our results suggest that ADM has an autocrine effect on Leydig cell steroidogenesis, possibly by interacting with EDN1 and under the control of gonadotropin. We propose that there is an ADM/EDN1 local regulatory mechanism that may be important in modulating the control of testicular functions by gonadotropins.

adrenomedullin, endothelin 1, Leydig cells, testis

¹Supported by grant HKU 7451/04M from the Research Grants Council of Hong Kong and a merit award from the University of Hong Kong.

Correspondence: ²Fai Tang, Department of Physiology, Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong, China. FAX: 852 28559730; e-mail: HUftang{at}hkucc.hku.hku

This article has been cited by other articles:

				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]