Ion dependence of resting membrane potential of rat spermatids

The membrane potential of rat spermatids was estimated as \m=-\22\m=+-\2 mV (mean \m=+-\sem) using three independent methods: using oxonol as a fluorescent membrane potential sensitive probe, from the passive distribution of hydrogen ions and from whole-cell patch-clamp records. The estimated permeability ratios Pk +:PCl\m=-\ and PNa+:PCl\m=-\ of the plasma membrane of rat spermatids were 1.0 and 0.3, respectively. These data indicate that the high luminal K+ concentration found in seminiferous tubules could partially close voltage-sensitive calcium channels in these cells.