Electrophoretic characteristics of ram and rabbit spermatozoa

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Abstract
1. The influence of a d. c. electric field on the direction in which ram and rabbit spermatozoa swim has been investigated. The magnitude of the electrophoretic component is so small in the presence of high salt concentrations (μ= 0.1) that it plays no part in controlling the direction in which the spermatozoa swim. A significant electrophoretic velocity component can, however, be imposed if the spermatozoa are suspended in a diluent (277 mM-fructose) with a low ionic strength (μ< 0.01). In this condition higher field strengths can be applied without any concomitant rise in temperature, and the ζ-potential increases because the gegen-ion concentration is reduced. 2. In a diluent containing 277 mM-fructose and 10 mM-NaCl two types of spermatozoa are seen when the electric field is applied. Their orientation depends on whether they carry a net negative charge in the region of their heads or their tails. 'Head-anode' spermatozoa swim with unusual rapidity towards the anode but immediately decelerate when the field is switched off. ‘Tail-anode' spermatozoa have a variable ground speed and may, if the field strength is high, be seen swimming tail first towards the anode. They accelerate away from the anode when the field is switched off. 3. The proportions of the two types of spermatozoa vary with salt concentration at constant pH, and with pH at constant salt (10 mM-NaCl) concentration. 4. If the swimming speed of spermatozoa is reduced by cooling, electrophoresis in the presence of high salt concentration (μ= 0.1) differentiates spermatozoa into two kinds in another way. Both are oriented with their tails pointing towards the anode (tail-anode), but their net ground speed may vary in magnitude and direction according to their inherent swimming speed. Complete immobilization of the spermatozoa resulted in a uniform electrophoretic migration towards the anode, tail first, at all pH’s above 3.5. 5. The implications of these findings are discussed with respect to sperm phenotypes and their possible electrophoretic separation.

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