A dihydropyridine-sensitive T-type Ca2+ current is the main Ca2+ current carrier in mouse primary spermatocytes.
Ca2+ entry through Ca2+ channels is likely to play an important role in the differentiation of male germ cells as well as in fertilization by mature sperm. Here we present a detailed analysis of Ca2+ currents expressed in acutely dissociated mouse primary spermatocytes. Patch-clamp recordings demonstrated that the only voltage-gated Ca2+ channels present belong to the family of T-type Ca2+ currents. Accordingly, Ni2+ (200 microM) and amiloride (500 microM) reduced current amplitude by 75 and 62%, respectively. To our knowledge, this is the first report of a system where T-type Ca2+ channels are expressed in isolation. Unexpectedly, 5 and 10 microM nifedipine also reduced peak currents by 38 and 53%, respectively significant inhibition of the Ca2+ current occurred at concentrations as low as 2 microM. Because mature sperm cells are unable to synthesize new proteins, these Ca2+ channels are also likely to be present in these cells, where they may contribute to the Ca2+ influx required to trigger the acrosome reaction. This notion is supported by the fact that concentrations of Ni2+ and nifedipine, which block these Ca2+ currents, also inhibit the acrosome reaction. Because these channels represent the primary pathway for voltage-gated Ca2+ entry in mouse spermatocytes, they may also participate in regulating meiotic cell division and sperm differentiation.
Santi
C M
CM
Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, DF.
Darszon
A
A
Hernández-Cruz
A
A
D000177:Acrosome / Q000187:drug effects / Q000502:physiology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D020746:Calcium Channels, L-Type; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D009532:Nickel / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D012671:Seminiferous Tubules / Q000502:physiology; D013090:Spermatocytes / Q000166:cytology / Q000502:physiology*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D000584:Amiloride; D009532:Nickel; D009543:Nifedipine; D002118:Calcium