title: Sodium and epithelial sodium channels participate in the regulation of the capacitation-associated hyperpolarization in mouse sperm.
abstract: In a process called capacitation, mammalian sperm gain the ability to fertilize after residing in the female tract. During capacitation the mouse sperm plasma membrane potential (E(m)) hyperpolarizes. However, the mechanisms that regulate sperm E(m) are not well understood. Here we show that sperm hyperpolarize when external Na(+) is replaced by N-methyl-glucamine. Readdition of external Na(+) restores a more depolarized E(m) by a process that is inhibited by amiloride or by its more potent derivative 5-(N-ethyl-N-isopropyl)-amiloride hydrochloride. These findings indicate that under resting conditions an electrogenic Na(+) transporter, possibly involving an amiloride sensitive Na(+) channel, may contribute to the sperm resting E(m). Consistent with this proposal, patch clamp recordings from spermatogenic cells reveal an amiloride-sensitive inward Na(+) current whose characteristics match those of the epithelial Na(+) channel (ENaC) family of epithelial Na(+) channels. Indeed, ENaC-alpha and -delta mRNAs were detected by reverse transcription-PCR in extracts of isolated elongated spermatids, and ENaC-alpha and -delta proteins were found on immunoblots of sperm membrane preparations. Immunostaining indicated localization of ENaC-alpha to the flagellar midpiece and of ENaC-delta to the acrosome. Incubations known to produce capacitation in vitro or induction of capacitation by cell-permeant cAMP analogs decreased the depolarizing response to the addition of external Na(+). These results suggest that increases in cAMP content occurring during capacitation may inhibit ENaCs to produce a required hyperpolarization of the sperm membrane.
authors.affiliation: Department of Veterinary and Animal Science, Paige Laboratories, University of Massachusetts, Amherst, MA 01003, USA.
authors.forename: Enrique O
authors.initials: EO
authors.lastname: Hernández-González
authors.forename: Julian
authors.initials: J
authors.lastname: Sosnik
authors.forename: Jennifer
authors.initials: J
authors.lastname: Edwards
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Acevedo
authors.forename: Irene
authors.initials: I
authors.lastname: Mendoza-Lujambio
authors.forename: Ignacio
authors.initials: I
authors.lastname: López-González
authors.forename: Ignacio
authors.initials: I
authors.lastname: Demarco
authors.forename: Eva
authors.initials: E
authors.lastname: Wertheimer
authors.forename: Alberto
authors.initials: A
authors.lastname: Darszon
authors.forename: Pablo E
authors.initials: PE
authors.lastname: Visconti
mesh_terms: D000584:Amiloride / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D053503:Epithelial Sodium Channels; D005260:Female; D006863:Hydrogen-Ion Concentration; D008297:Male; D008536:Meglumine / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D012964:Sodium / Q000378:metabolism*; D026941:Sodium Channel Blockers / Q000737:chemistry / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D013075:Sperm Capacitation; D013094:Spermatozoa / Q000166:cytology / Q000378:metabolism*
chemical_list: D053503:Epithelial Sodium Channels; D020033:Protein Isoforms; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D008536:Meglumine; D000584:Amiloride; D012964:Sodium; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases