Polarized distribution of NHE1 and NHE2 in the rat epididymis

Previous studies from our laboratory have provided evidence that the rat ep ididymis utilizes the Na+/H+ exchanger to transport acid and base. The pres ent study was undertaken to use immunohistochemistry for investigating the localization (apical versus basolateral) and distribution of NHE1 and NHE2 proteins along intact rat epididymis. Both proteins were found to be exclus ively localized within the epithelium. Immunoreactivity for NHE1 was detect ed on the basolateral surface, whereas NHE2 immunoreactivity was detected o n the apical side of the epithelium. Interestingly, NHE1 was found along th e entire length of the epididymal tubule whereas NHE2 was absent in the ini tial segment but present in the caput, corpus, and cauda regions. These res ults, when interpreted along with those of previous functional studies, may suggest that the apical NHE2 is involved in Na+ reabsorption and the basol ateral NHE1 in HCO3- secretion in the rat epididymis.