Ion dependence of resting membrane potential of rat spermatids

The membrane potential of rat spermatids was estimated as -22 +/- 2 mV (mean +/- 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- and PNa+:PCl- 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.