Cation and anion channels in rat and human spermatozoa

Ionic fluxes are thought to be important in the initiating process of gamete interaction such as acrosome reaction. Different populations of ion channels in rat and human spermatozoa were investigated using the planar lipid bilayer technique. Membrane proteins were isolated from rat and human sperm and inserted into lipid bilayer via fusion. We observed K(+) selective and Na(+)-selective channels, as well as divalent permeable cation channels in membrane preparations from rat sperm K+ channels, which were sensitive to the K+ channel blocker, tetraethylammonium (0.1 mM), exhibited a mean single channel conductance of 24 pS. Whereas, larger conductance, 109 pS, was found to be associated with Na+ channels. Low conductance anion channel, 15 pS, was also observed when permeant cations in the bathing solutions were substituted with N-methyl-D-glucamine leaving Cl- as the major permeant ion species. This channel exhibited a slower channel open and closed kinetics when compared to other cation channels. Both cation and anion channels with characteristics similar to that found in rat sperm were also observed in preparations from human sperm. The variety in the types of ion channels observed in rat and human spermatozoa suggests that ion channels may play different roles in sperm physiology and gamete interaction.