Electrical control of flagellar activity in impaled bull spermatozoa

The control of bull spermatozoon flagellar activity has been investigated using direct current injection into the cells through an impaling glass microelectrode. Negative current injection results in a decrease in the flagellar frequency. Flagellar frequencies can be decreased to zero with high negative currents. This current injection response is dependent on the magnesium concentration available to the spermatozoon interior. The current injection response is nearly independent of ATP concentrations. Resistance measurements indicate that the current injection pathway has a resistance of about 200 +/- 300 k omega, and that the current flowing through the cell membrane is not exceedingly large. Measurements of the induced potentials indicate transmembrane potentials during current injection of about -35 +/- 30 mV per microA of injected current. The results are compatible with an active transport process in bull spermatozoa that controls the flagellar activity in response to current injection by decreasing the internal Mg2+ concentrations during the injection of current.