These proton-secreting cells are often referred to as ‘‘mitochondria-rich cells’’.
Previous studies have localized H+-ATPase to specific epithelial cell types in all regions of the epididymis; these are apical (or narrow) cells within the initial segment region, and clear (or light) cells within the caput, corpus, and cauda regions of the epididymis. The timing of postnatal differentiation of narrow and clear cells has been assessed primarily by electron microscopy, and they are fully differentiated around the time of sexual maturation (~42 days) in the rat.
Our further studies on postnatal expression of H+-ATPase in the rat epididymis have shown that cells rich in H+-ATPase are not present immediately after birth and that at Postnatal Day 14, cells that express H+-ATPase are still rare in the epididymis, although they are readily detected in the vas deferens. H+-ATPase reaches its peak level of expression in the epididymis at 34 wk after birth. The factors that regulate the postnatal maturation of the cell types that express H+-ATPase within the epididymis are not fully understood.