Description:

Active transepithelial acid/base transport mechanisms establish and maintain a luminal acidic environment in the excurrent ducts of the male reproductive tract. Low luminal pH and bicarbonate concentrations are important for sperm maturation, and for maintaining sperm in a quiescent state during storage in the epididymis (Epid) and vas deferens (VD). Despite this critical function, acidification processes in the male reproductive tract are still incompletely understood.
A novel physiological approach using the self-referencing proton-selective electrode at the BioCurrrents Research Center, has allowed us to identify the major proton secretory mechanism in the VD. We have shown that a bafilomycin-sensitive, proton-pumping H⁺ATPase is concentrated in the apical membrane of a subpopulation of epithelial cells (clear cells) and is a major contributor to luminal acidification. The major goals of this study are to understand how defective acidification may impair reproductive function in pathologic states, and how intervention to manipulate acidification may eventually be used to control male fertility. Our specific aims are: 1) to define and characterize the complete pathways of proton secretion by the PP-rich cells; 2) to elucidate the mechanisms of vesicle recycling underlying the regulation of proton secretion; and 3) to examine the effect of some environmental pollutants on proton secretion.

Progress:

We are currently studying the potential role of the actin cytoskeleton in the modulation of proton secretion in the male reproductive tract. We have shown that the actin severing protein, gelsolin, is highly expressed in H⁺ATPase-rich cells of the Epid and VD. In rat VD isolated in vitro and cut open to expose the apical surface of the epithelium, the actin polymerizing agent, jasplakinolide, inhibited proton secretion, detected using the self-referencing H⁺-selective electrode. Western blot showed that jasplakinolide-treated VD have larger amounts of F-actin than controls. These results indicate that the active recycling of H⁺ATPase is regulated by luminal pH, and that modulation of the actin cytoskeleton, via gelsolin, is likely to participate in the regulation of H⁺ATPase recycling and net proton secretion in the Epid and VD.