Ionic regulation of the plasma membrane potential of rainbow trout (Salmo gairdneri) spermatozoa: role in the initiation of sperm motility.
The ionic dependence of the trout sperm plasma membrane potential was analysed by measuring the accumulation of the lipophilic ions 3H-tetraphenylphosphonium (TPP) and 14C-thiocyanate (SCN) following dilution in artificial media isotonic to the seminal fluid. Our data showed that the trout sperm plasma membrane has a mixed conductance: the plasma membrane potential is sensitive upon the transmembrane gradients of K+, Na+, and H+. This potential is negative (less than -40 mV) in a 125 mM choline chloride media (ChM) at pH 8.5. Replacement of choline by sodium has a small depolarizing effect. The membrane potential is about -15 mV in a 125 mM potassium chloride and falls near zero mV only if valinomycin is added. In ChM changing the external pH (pHe) greatly affects the membrane potential: its value rises from less than -40 mV at pHe 9.0 to -17 mV at pHe 5.0. This pH effect is observed also in presence of sodium or potassium. A decrease in the transmembrane proton gradient produced by increasing internal pH without changing pHe induces also a depolarisation of the plasma membrane. In the different media in which trout sperm remain immotile after dilution (media with [K+] greater than 20-40 mM or a pH less than 7.5) the plasma membrane is more depolarized than in media allowing motility, suggesting a relationship between the state of membrane polarization and the intracellular effectors of the axonemal movement.
Gatti
J L
JL
Laboratoire de Physiologie de la Reproduction, INRA, Nouzilly, France.
Billard
R
R
Christen
R
R
D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000493:pharmacokinetics; D002250:Carbon Radioisotopes; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D006859:Hydrogen / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009861:Onium Compounds / Q000378:metabolism / Q000493:pharmacokinetics; D009943:Organophosphorus Compounds / Q000378:metabolism / Q000493:pharmacokinetics; D011188:Potassium / Q000494:pharmacology; D012487:Salmonidae / Q000502:physiology*; D012964:Sodium / Q000494:pharmacology; D013081:Sperm Motility / Q000502:physiology; D013094:Spermatozoa / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D013861:Thiocyanates / Q000378:metabolism / Q000493:pharmacokinetics; D014316:Tritium; D014337:Trout / Q000502:physiology*
D000970:Antineoplastic Agents; D002250:Carbon Radioisotopes; D007477:Ions; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D013861:Thiocyanates; D014316:Tritium; D006859:Hydrogen; D012964:Sodium; D011188:Potassium; C013289:tetraphenylphosphonium