The relationship between membrane status and fertility of boar spermatozoa after flow cytometric sorting in the presence or absence of seminal plasma.
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The motility, viability (percent live), capacitation status and in vitro fertility of boar spermatozoa were examined, after staining with Hoechst 33,342 and flow cytometric sorting in the absence or presence of seminal plasma. Viability was higher in unstained controls and when seminal plasma was present in the medium used to collect spermatozoa from the cell sorter than when seminal plasma was absent or in the staining extender only, but motility was highest when seminal plasma was included in the extender only, compared with the controls and other treatments. The proportions of capacitated spermatozoa were increased by sorting, but were lower when seminal plasma was present, rather than absent, from the staining extender and the collection medium. Compared with unstained controls, extension and staining without sorting only increased the proportion of capacitated spermatozoa after washing in preparation for in vitro fertilization. The percentages of polyspermic, penetrated and cleaved oocytes were lower when inseminated with unsorted (stained) than control (unstained) spermatozoa, regardless of the presence or absence of seminal plasma. These parameters were higher for sorted than for control spermatozoa in the absence of seminal plasma, but in its presence penetration and cleavage were substantially lower. The proportions of capacitated spermatozoa were lower when seminal plasma was present in the collection medium only than in the staining extender or when it was absent altogether, but the former treatment substantially reduced the proportions of polyspermic, penetrated and cleaved oocytes, and the proportion of blastocysts. These findings indicate that sperm capacitation associated with flow cytometric sorting can be reduced by the inclusion of seminal plasma in the collection medium, but this treatment reduces the ability of spermatozoa to fertilize oocytes in vitro under these conditions.