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 P-K+:P-Cl- and P-Na+:P-Cl- 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.