Mouse sperm membrane potential: changes induced by Ca2+.
Mouse sperm resting membrane potential (Er) (-42 +/- 8.8 mV), determined with a potential sensitive dye, depended on extracellular K+ and, in the absence of extracellular Ca2+ ([Ca2+]e), on external Na+ ([Na+]e). Ca2+ addition (> 5 microM) to sperm in Ca-free media induced a transient hyperpolarization (Ca-ith) which strongly depended on [Na+]e and less on external Cl- ([Cl-]e). Cd2+ and Mn2+ (microM) mimicked the Ca2+ effect, but not Ba2+. The Ca-ith was partially inhibited by ouabain (74%, IC50 = 5.8 microM) and niflumic acid (38%, IC50 = 240 microM), indicating the participation of the Na-K ATPase and Cl- channels. In Ca-free low-Na+ media, Ca2+ addition caused a depolarization sensitive to: nimodipine (25 microM), trifluoperazine (12.5 microM) and Mg2+ (1.2 mM), suggesting the participation of Ca2+ channels. Since some inhibitors of the sperm Ca-ith block the acrosome reaction (AR), both processes may share transport systems.
Espinosa
F
F
Depto. Genética y Fisiología Molecular, Universidad Nacional Autónoma de México, Morelos.
Darszon
A
A
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000494:pharmacology*; D002712:Chlorides / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000494:pharmacology; D008564:Membrane Potentials / Q000502:physiology; D008670:Metals / Q000494:pharmacology; D051379:Mice; D008815:Mice, Inbred Strains; D009544:Niflumic Acid / Q000494:pharmacology; D009553:Nimodipine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013094:Spermatozoa / Q000502:physiology*; D014268:Trifluoperazine / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology
D002712:Chlorides; D008670:Metals; D014634:Valinomycin; D014268:Trifluoperazine; D008345:Manganese; D009544:Niflumic Acid; D009553:Nimodipine; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D002118:Calcium