After ejaculation, spermatozoa undergo a series of transformation in the female genital tract, named capacitation, that enables them to bind to the zona pellucida, initiate the acrosome reaction and fertilize the egg. Mammalian sperm motility, capacitation and acrosome reaction are regulated by signal transduction systems involving cAMP and cAMP-dependent protein kinase A (PKA). Intracellular levels of cAMP are regulated by adenylyl cyclase (AC) and phosphodiesterases (PDEs), responsible for its production and degradation, respectively. Of the 11 PDE families that exist, calmodulin (CaM)-dependent PDE (PDE1) and cAMP-specific PDE (PDE4) activities were previously identified in human spermatozoa. The aims of the present study were to evaluate the role played by some PDEs in human sperm function, to determine which PDEs are present and to evaluate the changes in cAMP, PDE and PKA activities during sperm capacitation and acrosome reaction. PDE activity did not change during either capacitation or acrosome reaction while PKA activity was increased in both phenomena. Moreover, sperm PDEs were associated with the membrane (50--60%) as well as with the particulate fraction (30--50%) and had much more affinity for cAMP than cGMP as substrate. Type-specific PDE inhibitors such as EHNA for cGMP-stimulated PDE (PDE2), milrinone for cGMP-inhibited PDE (PDE3) and rolipram for PDE4 but not sildenafil for cGMP-specific PDE (PDE5), decreased sperm PDE activity suggesting that PDE2, PDE3 and PDE4 but not PDE5 were present both in membrane and particulate fractions. Moreover, EHNA and rolipram increased sperm capacitation while milrinone increased sperm cAMP. Anti-PDE1A and anti-PDE3A antibodies recognized proteins of 67 kDa (PDE1A) and 97 kDa (PDE3A). Immunolocalization indicated that PDE1A was present on the equatorial segment of the sperm head as well as on the mid- and principal pieces of the flagellum and that PDE3A was present on the post-acrosomal segment of the head. Furth
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.38498 |
| Date | January 2002 |
| Creators | Lefièvre, Linda |
| Contributors | Gagnon, Claude (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Division of Surgical Research.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001941274, proquestno: NQ85720, Theses scanned by UMI/ProQuest. |
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