HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 80/1/134    most recent biolreprod.108.070797v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Belleannée, C. Articles by Breton, S. Search for Related Content PubMed PubMed Citation Articles by Belleannée, C. Articles by Breton, S. Agricola Articles by Belleannée, C. Articles by Breton, S.

Segmental Expression of the Bradykinin Type 2 Receptor in Rat Efferent Ducts and Epididymis and Its Role in the Regulation of Aquaporin 9¹

Center for Systems Biology,³ Program in Membrane Biology/Nephrology Division, Massachusetts General Hospital, Boston, Massachusetts 02114 Groupe d'Étude des Protéines Membranaires,⁴ Université de Montréal, Montréal, Québec, Canada H3C 3J7

ABSTRACT

Water and solute transport in the efferent ducts and epididymis are important for the establishment of the appropriate luminal environment for sperm maturation and storage. Aquaporin 9 (AQP9) is the main water channel in the epididymis, but its regulation is still poorly understood. Components of the kinin-kallikrein system (KKS), leading to the production of bradykinin (BK), are highly expressed in the lumen of the male reproductive tract. We report here that the epididymal luminal fluid contains a significant amount of BK (2 nM). RT-PCR performed on epididymal epithelial cells isolated by laser capture microdissection (LCM) showed abundant BK type 2 receptor (Bdkrb2) mRNA expression but no type 1 receptor (Bdkrb1). Double-immunofluorescence staining for BDKRB2 and the anion exchanger AE2 (a marker of efferent duct ciliated cells) or the V-ATPase E subunit, official symbol ATP6V1E1 (a marker of epididymal clear cells), showed that BDKRB2 is expressed in the apical pole of nonciliated cells (efferent ducts) and principal cells (epididymis). Triple labeling for BDKRB2, AQP9, and ATP6V1E1 showed that BDKRB2 and AQP9 colocalize in the apical stereocilia of principal cells in the cauda epididymidis. While uniform Bdkrb2 mRNA expression was detected in the efferent ducts and along the epididymal tubule, marked variations were detected at the protein level. BDKRB2 was highest in the efferent ducts and cauda epididymidis, intermediate in the distal initial segment, moderate in the corpus, and undetectable in the proximal initial segment and the caput. Functional assays on tubules isolated from the distal initial segments showed that BK significantly increased AQP9-dependent glycerol apical membrane permeability. This effect was inhibited by BAPTA-AM, demonstrating the participation of calcium in this process. This study, therefore, identifies BK as an important regulator of AQP9.

bradykinin receptor, efferent ducts, epididymis, male reproductive tract, water channel

¹Supported by National Institutes of Health grant HD045821 to S.B. The work performed in the Microscopy Core Facility of the Massachusetts General Hospital Program in Membrane Biology was supported by Center for the Study of Inflammatory Bowel Disease grant DK43351 and Boston Area Diabetes and Endocrinology Research Center award DK57521.

Correspondence: ²Sylvie Breton, Program in Membrane Biology, Simches Research Center, Massachusetts General Hospital, 185 Cambridge Street, CPZN 8.204, Boston, MA 02114. FAX: 617 643 3182; e-mail: breton.sylvie{at}mgh.harvard.edu