Mouse sperm patch‐clamp recordings reveal single Cl⁻ channels sensitive to niflumic acid, a blocker of the sperm acrosome reaction

Abstract

Ion channels lie at the heart of gamete signaling. Understanding their regulation will improve our knowledge of sperm physiology, and may lead to novel contraceptive strategies. Sperm are tiny (V3 W Wm diameter) and, until now, direct evidence of ion channel activity in these cells was lacking. Using patchclamp recording we document here, for the first time, the presence of cationic and anionic channels in mouse sperm. Anion selective channels were blocked by niflumic acid (NA) (IC SH = 11 W WM). The blocker was effective also in inhibiting the acrosome reaction induced by the zona pellucida, GABA or progesterone. These observations suggest that Cl 3 channels participate in the sperm acrosome reaction in mammals.z 1998 Federation of European Biochemical Societies.

Activation of GABAAReceptor/Cl−Channel and Capacitation in Rat Spermatozoa: HCO3−and Cl−are Essential

“…For example, the sperm cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-activated Cl À channel which is involved in the transport of HCO 3 À that is important for sperm capacitation and fertilization [Hernandez-Gonzalez et al 2007;Xu et al 2007]. In addition, Cl À has been reported to be required for the progesterone-, GABA-and zona pellucid-initiated acrosome reaction in mouse, porcine, hamster and human spermatozoa [Espinosa et al 1998;Melendrez and Meizel 1995;Shi et al 1997;Wistrom and Meizel 1993;Yashimatsu and Yanagimachi 1988]. However, it is not clear whether extracellular Cl À is required for sperm capacitation and hyperactivated motility.…”

Cl− Channels and Transporters in Sperm Physiology

“…NFA also partially inhibited a Ca 2+ -induced hyperpolarization partially driven by Cl − in mouse spermatozoa (Espinosa et al 1998 ). Anion channel blockers such as NFA, for example, DIDS, also inhibit the mouse and human sperm AR, as well as Cl − channels detected in these cells (Espinosa and Darszon 1995 ;Espinosa et al 1998 ;Figueiras-Fierro et al 2013 ;Orta et al 2012 ).…”

“…Much less is known about how Cl − movements infl uence this event. Interestingly, nifl umic acid (NFA), best known as a Ca 2+ -activated Cl − channel inhibitor, was reported a long time ago to block the fi rst Cl − single-channel activity recorded in mammalian sperm as well as the AR induced by solubilized ZP, progesterone, and GABA in mouse sperm (Espinosa et al 1998 ). NFA also partially inhibited a Ca 2+ -induced hyperpolarization partially driven by Cl − in mouse spermatozoa (Espinosa et al 1998 ).…”

“…Interestingly, nifl umic acid (NFA), best known as a Ca 2+ -activated Cl − channel inhibitor, was reported a long time ago to block the fi rst Cl − single-channel activity recorded in mammalian sperm as well as the AR induced by solubilized ZP, progesterone, and GABA in mouse sperm (Espinosa et al 1998 ). NFA also partially inhibited a Ca 2+ -induced hyperpolarization partially driven by Cl − in mouse spermatozoa (Espinosa et al 1998 ). Anion channel blockers such as NFA, for example, DIDS, also inhibit the mouse and human sperm AR, as well as Cl − channels detected in these cells (Espinosa and Darszon 1995 ;Espinosa et al 1998 ;Figueiras-Fierro et al 2013 ;Orta et al 2012 ).…”

“…The initial patch-clamp recordings directly on epididymal mouse sperm revealed an anion channel displaying biophysical properties and sensitivity to NFA, resembling to the Ca 2+ -dependent Cl − channels (Espinosa et al 1998 ;Hogg et al 1994 ). Thereafter, a Cl − -permeable channel showing long stable openings was documented in patch-clamp studies in the cell-attached mode in the human sperm.…”