An apical membrane Na+/H+ exchanger isoform, NHE-3, is present in the rat epididymal epithelium.
An acidic milieu is required for sperm maturation and for keeping sperm quiescent during storage in the cauda epididymidis. Previous studies have implicated a Na+/H+ exchanger (NHE) in epididymal acidification together with carbonic anhydrase (CA) and vacuolar proton adenosine triphosphatase (H(+)-ATPase). The present studies were undertaken to discover whether the NHE isoform involved is NHE-3, which is known to mediate Na+ and HCO3- absorption in renal tubules. Using the reverse transcription polymerase chain reaction technique (RT-PCR), Northern blot analysis and in situ hybridization, NHE-3 mRNA was detected mainly in the cauda epididymis and to a lesser extent in other regions of the epididymis. Immunohistochemical studies showed that NHE-3 was present in the apical membranes of the epithelial principal cells and confirmed that its expression is strongest in the cauda region, decreasing towards the more proximal regions. Immunoblotting showed a similar expression pattern. These results demonstrate that NHE-3 is expressed in the rat epididymal duct with strongest expression in its cauda region. These findings are thus consistent with the possibility that NHE-3 in the epididymal duct is involved in luminal Na+ and/or HCO3- absorption, as in the renal proximal tubule, and thereby in the regulation of sperm motility and maturation.
Kaunisto
K
K
Department of Anatomy and Cell Biology, P.O. Box 5000, FIN-90014 University of Oulu, Finland. Kari.Kaunisto@oulu.fi
Moe
O W
OW
Pelto-Huikko
M
M
Traebert
M
M
Rajaniemi
H
H
D000818:Animals; D015152:Blotting, Northern; D002462:Cell Membrane / Q000378:metabolism; D004822:Epididymis / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
D012333:RNA, Messenger; C000613387:Slc9a3 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers