The role of anion channels and Ca2+ in addition to K+ channels in the physiological volume regulation of murine spermatozoa

CH Yeung, JP Barfield… - Molecular Reproduction …, 2005 - Wiley Online Library
CH Yeung, JP Barfield, TG Cooper
Molecular Reproduction and Development: Incorporating Gamete Research, 2005Wiley Online Library
Studies in the human, transgenic mice, and cattle indicate that sperm cell volume regulation
plays an important role in male fertility as spermatozoa encounter a hypo‐osmotic challenge
upon ejaculation into the female tract. Physiological regulatory volume decrease (RVD) was
examined using flow cytometry in murine sperm released into incubation medium mimicking
uterine osmolality and including putative channel inhibitors. The involvement of K+ channels
was indicated by the recovery of volume regulation by the K+ ionophore valinomycin in …
Abstract
Studies in the human, transgenic mice, and cattle indicate that sperm cell volume regulation plays an important role in male fertility as spermatozoa encounter a hypo‐osmotic challenge upon ejaculation into the female tract. Physiological regulatory volume decrease (RVD) was examined using flow cytometry in murine sperm released into incubation medium mimicking uterine osmolality and including putative channel inhibitors. The involvement of K+ channels was indicated by the recovery of volume regulation by the K+ ionophore valinomycin in defective sperm from infertile transgenic mice, and from blockage of RVD by quinine in normal sperm. However, in neither case was the recovery complete. The involvement of volume‐sensitive osmolyte and anion channels (VSOAC) were investigated using blockers effective in other cell types. NPPB (5‐nitro‐2(3‐phenylpropylamino) benzoic acid) and tamoxifen inhibited RVD but SITS (4‐acetamido‐4′‐isothiocyanato‐stilbene‐2,2′‐disulphonic acid) at 0.4 and 1 mM had no effect whereas DIDS (di‐isothiocyanato‐stilbene‐2,2′‐disulphonic acid) at 1 mM enhanced RVD. Verapamil, but not another P‐glycoprotein antagonist cyclosporin, caused sperm swelling which persisted in the presence of valinomycin, in Ca2+‐free medium and in the presence of thapsigargin, but swelling was abolished by the Ca2+ ionophore A23187. Nifedipine was slightly effective in blocking RVD. Analysis by Western blotting failed to reveal ClC‐2 and ClC‐3 members of the chloride channel family in murine or rat sperm proteins despite signal bands in positive tissue controls. These findings implicate the involvement of some unidentified VSOAC in sperm volume regulation, which is probably Ca+‐dependent. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
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