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1 May 2000 Induction of a Sodium Ion Influx by Progesterone in Human Spermatozoa
Catherine Patrat, Catherine Serres, Pierre Jouannet
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In human spermatozoa, progesterone (P4) induces a depolarization of the plasma membrane, a rapid calcium (Ca2 ) influx, and a chloride efflux. The sodium ion (Na ) was partly responsible for the P4-induced depolarizing effect but was not required for calcium influx. We used fluorescent probes for spectrofluorometry to investigate whether P4 induced a Na influx and whether voltage-operated channels were involved in Na and/or Ca2 entries. We found that 10 μM P4 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 μM flunarizine, a Na and Ca2 voltage-dependent channel blocker, inhibited the sodium influx induced by 10 μM P4 by 84.6 ± 15.4%. The Ca2 influx induced by 10 μM P4 was also significantly inhibited in a Na -containing medium by 10 μM flunarizine or 10 μM pimozide (P < 0.01). In contrast, flunarizine had no inhibitory effect on the Ca2 influx induced by 10 μM P4 in spermatozoa incubated in Na -depleted medium. The P4-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 P4 stimulates a Na influx that could be involved in the AR completion. They also suggest that voltage-dependent Na and Ca2 channels are implicated in P4-mediated signaling pathway in human spermatozoa.

Catherine Patrat, Catherine Serres, and Pierre Jouannet "Induction of a Sodium Ion Influx by Progesterone in Human Spermatozoa," Biology of Reproduction 62(5), 1380-1386, (1 May 2000).
Received: 3 August 1999; Accepted: 1 December 1999; Published: 1 May 2000
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