Effects of seminal fluid fractions on plasma and acrosome membrane integrity and mitochondrial membrane potential determined by flow cytometry in chilled canine spermatozoa.

Depending on the mammal species, the use of seminal plasma during semen processing for cryopreservation has been found to have both beneficial and detrimental effects. This study was designed to determine the effects of the second (SF) and third[prostatic fluid, (PF)] ejaculate fractions on plasma membrane and acrosome integrity, mitochondrial membrane potential(Δψm), phosphatidylserine (PS) translocation and sperm motility in chilled canine spermatozoa by flow cytometry. After pooling the second sperm-rich fraction of ejaculates from six dogs, samples for each assay were preserved at 5C for 72 h in egg yolk-TRIS extender (EYT) alone (control) or supplemented with seminal fluid from the second (EYT-SF) or third (EYT-PF) ejaculated fractions. After cold storage,groups EYT-SF and EYT-PF showed significantly higher percentages of sperm cells with an intact acrosome[68.8 ± 1.4%, 69.6 ± 2.6% (p < 0.01)] and intact plasma membrane [48.1 ± 2.8%, 50.4 ± 8.2% (p < 0.001)] than that observed in EYT [51.7 ± 3.2% and 33.3 ± 4.1%respectively]. Only in EYT-SF was PS translocation significantly reduced compared to EYT-PF and EYT [3.9 ± 0.4%,10.2 ± 2.2% and 9.0 ± 1.5%, respectively (p < 0.001)]. However, significantly diminished sperm motility was observed in EYT-SF and EYT-PF compared to EYT[36.8 ± 2.1%, 35.5 ± 2.3% and 78.4 ± 4.7% (p < 0.001)]. No significant differences were detected in Δψm (p > 0.05). In conclusion, supplementing semen extenders with seminal fluid from the second or third fractions of the ejaculate supplementation helps to preserve the integrity of the plasma and acrosome membranes along with the mitochondrial membrane potential but seems to compromise the motility of canine spermatozoa chilled for 72 h.