Acidification of the male reproductive tract by a proton pumping(H⁺)-ATPase

Abstract

An acidic luminal pH (ref. 1–3) is involved in sperm maturation, and in maintaining sperm in an immotile state in the epididymis and vas deferens^2,4–6. Neutralization by prostatic fluid is one of a complex series of events that triggers sperm motility^2,7,8. Failure of the acidification mechanism might, therefore, result in poor sperm maturation, premature motility and infertility. We have shown that a vacuolar (H⁺)–ATPase is expressed at high levels on the luminal plasma membrane of specialized cells in the epididymis⁹, which closely resemble acid–secreting kidney intercalated cells^10,11. We now show that similar cells are also present in the vas deferens, and that a bafilomycin–sensitive proton flux can be detected using a noninvasive proton–selective vibrating probe. Up to 80% of the net proton secretion in the vas deferens is inhibited by bafilomycin, consistent with a major role of a vacuolar–type (H⁺)–ATPase in this process. This acidification mechanism is a potential target for novel strategies aimed at modulating the acidification capacity of parts of the male reproductive tract and, therefore, in regulating male fertility.