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Sullivan, Robert

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Département d'obstétrique et de gynécologie, Faculté de médecine, Université Laval
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  • Publication
    Papaverine-sensitive phosphodiesterase activity is measured in bovine spermatozoa
    (Wiley, 2016-11-16) Vigneault, Christian; Poulin, Marie-Pier; Bergeron, Annick; Leclerc, Pierre; Richard, François J.; Sullivan, Robert; Hébert, Audrey; Guillemette, Christine; Aragon, Juan Pablo; Laroche, A.; Blondin, Patrick.
    Cyclic adenosine monophosphate (cAMP) plays a crucial role as a signaling molecule for capacitation, motility, and acrosome reaction in mammalian spermatozoa. It is well‐known that cAMP degradation by phosphodiesterase (PDE) enzyme has a major impact on sperm functions. This study was undertaken to characterize cAMP‐PDE activity in bovine spermatozoa. Total cAMP‐PDE activity in cauda epididymal and ejaculated spermatozoa was 543.2 ± 49.5 and 1252.6 ± 86.5 fmoles/min/106 spermatozoa, respectively. Using different family‐specific PDE inhibitors, we showed that in cauda epididymal and ejaculated spermatozoa, the major cAMP‐PDE activity was papaverine‐sensitive (44.5% and 57.5%, respectively, at 400 nm, papaverine is a specific inhibitor of the PDE10 family). These data are supporting the functional presence of PDE10 in bovine spermatozoa and were further confirmed by western blot to be PDE10A. Using immunocytochemistry, we showed immunoreactive signal for PDE10A present on the post‐acrosomal region of the head and on the flagella of ejaculated spermatozoa. Using papaverine, we showed that it promotes tyrosine phosphorylation of sperm proteins, phosphorylation of Erk1 and Erk2, and Ca²+ release from Ca²+ store. These results suggest that PDE10 is functionally present in bovine spermatozoa and is affecting different molecular events involved in capacitation, most probably by cAMP local regulation.
  • Publication
    Characterization of cAMP-phosphodiesterase activity in bovine seminal plasma
    (American Society of Andrology, 2016-08-27) Bergeron, Annick; Richard, François J.; Sullivan, Robert; Hébert, Audrey; Guillemette, Christine; Aragon, Juan Pablo; Blondin, Patrick.
    The second messenger cyclic adenosine monophosphate (cAMP) has a central role in sperm physiology. Extracellular cAMP can besequentially degraded into 50AMP and adenosine by ecto-phosphodiesterases (ecto-PDE) and ecto-nucleotidases, a phenomenoncalled extracellular cAMP-adenosine pathway. As cAMP-adenosine pathway is involved in sperm capacitation, we hypothesize thatextracellular PDEs are functionally present in seminal plasma. Exclusively measuring cAMP-PDE activity, total activity in bovineseminal plasma was 10.1 1.5 fmoles/min/lg. Using different family-specific PDE inhibitors, we showed that in seminal plasma,the major cAMP-PDE activity was papaverine sensitive (47.5%). These data support the presence of PDE10 in bovine seminal plasmaand was further confirmed by western blot. In epididymal fluid, total cAMP-PDE activity was 48.2 14.8 fmoles/min/lg and weshowed that the major cAMP-PDE activity was 3-isobutyl-methylxanthine insensitive and thus ascribed to PDE8 family. PDE10AmRNAs were found in the testis, epididymis, and seminal vesicles. cAMP-PDE activity is present in bovine seminal plasma and epi-didymal fluid. The results suggest a role for ecto-PDEs present in those fluids in the signaling pathways involved in sperm functions.