RESISTANCE TO HYPEROSMOTIC STRESS IN BOAR SPERMATOZOA - THE ROLE OF THE IONIC PUMPS AND THE RELATIONSHIP WITH CRYOSURVIVAL

The resistance to changes in the osmolarity of boar sperm was used to measure the resistance of boar sperm cells against freezing/thawing. S emen was incubated for 5 min in different solutions ranging from about 600 mOsm to about 4000 mOsm, and at 4 degrees C, 16 degrees C or 37 d egrees C (undisturbed media), This undisturbed media was constituted b y NaCl, glycerol or glucose. This semen was then placed in an isoosmot ic solution (disrupted solutions). Incubation in undisturbed media did not alter the percentages of viability or altered acrosomes, except w hen the initial incubation has been at 37 degrees C and with osmolarit ies above 1000 mOsm. Viability and altered acrosome statistics were st rongly modified in disrupted media. These effects are dependent upon t he initial osmolarity of the media, but not upon the temperature. Pre- incubation with ouabain or amiloride did not affect spermatozoa incuba ted at 16 degrees C in a 2211 mOsm, NaCl medium. However, in sperm inc ubated in this 2211 mOsm medium, and then rapidly placed in an isoosmo tic solution, ouabain induced a decrease in viability and an increase in altered acrosomes. Amiloride did not affect the response of cells t o the disrupted medium. Some significant correlations were observed am ong the percentages of altered acrosomes after hyperosomotic stress an d some quality parameters of the fresh boar semen, especially the moti on parameters. Although the resistance to hyperosmotic stress could be a valuable parameter in assessing fresh semen quality analysis, its u sefulness in frozen-thawed semen is compromised, since other factors b eside osmotic changes an involved in the resistance of boar semen to f reezing-thawing. The Na+/K+, ouabain-dependent ATP-ase activity seems to be related to the mechanisms of resistance to hyperosmotic stress i n boar sperm. (C) 1997 Elsevier Science B.V.