Postnatal development of H(+)ATPase (proton-pump)-rich cells in rat epididymis

Active proton secretion and bicarbonate reabsorption by epithelial cells of the mammalian excurrent duct system maintains an acidic luminal pH that is involved in creating a suitable environment for sperm maturation and stora ge. Both an apical Na/H exchanger and an apical H(+)ATPase have been implic ated in luminal acidification. The H(+)ATPase is located in apical and/or n arrow cells in the caput epididymidis, and clear cells in the corpus and ca uda epididymidis. As a step toward understanding the acute and chronic regu lation of luminal acidification in excurrent ducts, we have followed the ap pearance of H(+)ATPase-rich cells in rat epididymis during postnatal develo pment, using antibodies to subunits of the H(+)ATPase. In addition, we perf ormed double staining with antibodies against carbonic anhydrase type II (C AII). H(+)ATPase-rich cells were already detectable 2 weeks after birth in all regions of the epididymis, and reached maximum numbers after 3-4 weeks. CAII-rich cells followed a similar developmental pattern. In adult rats, t he number of H(+)ATPase/CAII-positive cells in the cauda was on average mor e than double the number in the caput epididymidis, although considerable i ntertubule variability was seen in both regions. Double immunostaining show ed that CAII and H(+)ATPase were colocalized in the same cells in the caput and cauda, but H(+)ATPase-rich cells in the corpus contained low levels of CAII. These results demonstrate that differentiated subpopulations of prot on-secreting epithelial cells appear early during epididymal development, a nd that the induction of H(+)ATPase in these cells occurs prior to sexual m aturation.