Identification of calcium conducting channels in isolated boar sperm plasma membranes

Ion channel recordings were obtained from liposomes containing purified boar sperm plasma membrane proteins using a tip-dip method. Liposomes prepared in HEPES-TRIS and clamped by electrodes containing Ba-HEPES displayed channel activity that was partially inhibited by verapamil or nitrendipine and completely inhibited by La3+. Reversal of current at pipette negative voltages was observed only when Ba2+ ions were also present in the bath solution. These data indicate that channels capable of carrying calcium currents are prominent components of the plasma membrane of mammalian sperm.