A differential mechanism is involved during heparin- and cryopreservation-induced capacitation of XXXX spermatozoa.

@entity1 @entity6579 @entity10393 @entity7914 @entity291 @entity413
After ejaculation, @entity1 spermatozoa must undergo capacitation to fertilize. Capacitation of @entity291 spermatozoa occurs in vitro in medium supplemented with heparin. Semen cryopreservation is an important tool for assisted reproduction, although the fertility of frozen-thawed spermatozoa is reduced, possibly due to precocious capacitation-like changes that are known to occur. Our purpose was to clarify the mechanisms involved in bull sperm cryocapacitation induced by cryopreservation. Our general hypothesis is that the signaling pathways that lead to capacitation are triggered by the cryopreservation procedure. Ejaculated @entity291 semen was divided into two aliquots and diluted in extender; one was then kept fresh, whereas the second was cryopreserved. Western blots of extracted sperm proteins with anti- @entity10393 antibody showed that capacitation, induced by either heparin in fresh sperm or cryopreservation (cryocapacitation), is associated with a differential profile of @entity10393 -containing proteins. Immunolocalization of @entity10393 -containing proteins in the fresh and cryopreserved spermatozoa showed that, after thawing, cryocapacitated sperm displayed labeling over the acrosomal region, whereas for fresh sperm, this labeling appeared after 5-h incubation with heparin. The @entity7914 assay and the ability of the sperm to undergo the @entity6579 -induced acrosome reaction were used to confirm that a subpopulation of cryopreserved sperm is capacitated at thawing, irrespective of heparin inclusion. Since @entity413 is known to inhibit heparin-induced capacitation, the semen extender was modified to include @entity413 as a means of inhibiting cryocapacitation; however, cryocapacitation was not prevented according to the @entity7914 assay and profile of @entity10393 -containing sperm proteins.
