Studies of stallion sperm survival: preservation of progressive motility of stallion spermatozoa by low ionic strength media.

Preservation of stallion sperm forward motility was studied using a video recording system in semen diluted with media of different ionic strength and sodium content. After 8 hr of incubation at room temperature, semen diluted in a low ionic strength media containing sucrose displayed 65 +/- 9% motility with 68 +/- 3% of the motile sperm showing forward motility (diameter of head trajectory greater than or equal to 80 microns). In contrast, sperm populations diluted and incubated with a normal ionic strength media containing sodium had 56 +/- 7% motile sperm of which only 36 +/- 7% displayed forward progression. Replacement of the sodium ion in the normal ionic strength media by a different cation (choline) produced results similar to those of the media containing high sodium concentration. These results indicate that the preservation of stallion sperm progressive motility is highly dependent on the ionic strength of the media. Membrane depolarization caused by the replacement of ions by noncharged particles in the sperm's external medium might be responsible for the sustained coordination of the flagellar movements.