Induction of a sodium ion influx by progesterone in human spermatozoa.
In human spermatozoa, progesterone (P(4)) induces a depolarization of the plasma membrane, a rapid calcium (Ca(2+)) influx, and a chloride efflux. The sodium ion (Na(+)) was partly responsible for the P(4)-induced depolarizing effect but was not required for calcium influx. We used fluorescent probes for spectrofluorometry to investigate whether P(4) induced a Na(+) influx and whether voltage-operated channels were involved in Na(+) and/or Ca(2+) entries. We found that 10 microM P(4) significantly increased intracellular Na(+) concentration from 17.8 +/- 2.0 mM to 27.2 +/- 1. 6 mM (P < 0.001). Prior incubation of spermatozoa with 10 microM flunarizine, a Na(+) and Ca(2+) voltage-dependent channel blocker, inhibited the sodium influx induced by 10 microM P(4) by 84.6 +/- 15.4%. The Ca(2+) influx induced by 10 microM P(4) was also significantly inhibited in a Na(+)-containing medium by 10 microM flunarizine or 10 microM pimozide (P < 0.01). In contrast, flunarizine had no inhibitory effect on the Ca(2+) influx induced by 10 microM P(4) in spermatozoa incubated in Na(+)-depleted medium. The P(4)-promoted acrosome reaction (AR) was significantly higher when spermatozoa were incubated in Na(+)-containing medium as compared to Na(+)-depleted medium. These data demonstrate that P(4) stimulates a Na(+) influx that could be involved in the AR completion. They also suggest that voltage-dependent Na(+) and Ca(2+) channels are implicated in P(4)-mediated signaling pathway in human spermatozoa.
Patrat
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C
Service d'Histologie-Embryologie-Biologie de la Reproduction, Université Paris V-Cochin, 75014 Paris, France. catherine.patrat@cch.ap-hop-paris.fr
Serres
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C
Jouannet
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P
D020101:Acrosome Reaction / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D005109:Extracellular Matrix / Q000378:metabolism; D005444:Flunarizine / Q000494:pharmacology; D006801:Humans; D008297:Male; D010868:Pimozide / Q000494:pharmacology; D011374:Progesterone / Q000378:metabolism / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D026941:Sodium Channel Blockers; D013075:Sperm Capacitation / Q000187:drug effects; D013094:Spermatozoa / Q000187:drug effects* / Q000378:metabolism*
D002121:Calcium Channel Blockers; D026941:Sodium Channel Blockers; D010868:Pimozide; D011374:Progesterone; D012964:Sodium; D005444:Flunarizine; D002118:Calcium