Assessing equine sperm-membrane integrity

The swelling of cells in a hypoosmotic medium has been described as an impo rtant criterion for assessing the functional integrity of the sperm plasma membrane. The resistance of equine spermatozoa to osmolarity changes was st udied by extending 98 semen samples collected from nine stallions in media at five osmolarities (300, 200, 150, 100, and 50 mOsmoll(-1)). The response of the cells was measured by the spermatocrit technique and eosin staining . Spermatocrit determines the increase on spermatozoal volume under hypo-os motic conditions, a sign of functional integrity of sperm plasma membrane, whereas the eosin staining evaluates the viability of spermatozoa. A signif icant positive correlation (P < 0.01) was observed between spermatocrit val ues and percentage of eosin-unstained cells. Spermatocrit measurements and eosin staining proved to be useful methods to evaluate the integrity of spe rm plasma membrane under hypoosmotic conditions and could be used as an add itional criterion to predict semen preservation ability.