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.