Implication of calmodulin-dependent phosphodiesterase type 1 during bovine sperm capacitation.
Phosphodiesterases (PDEs) are enzymes that degrade cyclic nucleotides. The calcium-calmodulin dependent PDE type 1 (PDE 1) and the cyclic adenosine monophosphate (cAMP)-specific PDE type 4 (PDE 4) have been implicated in sperm function. We tested the hypothesis that specific PDEs regulate capacitation of bovine sperm in a manner independent of those that mediate motility. Our objectives were to determine the effects of inhibiting PDE 1 and PDE 4 on capacitation and motility, and to compare these effects to those of heparin, which is necessary for capacitation of bull sperm in vitro. Fresh sperm were supplemented either with 15 microg/mL heparin (positive control) or the PDE inhibitors vinpocetine (specific for PDE 1) and rolipram (specific for PDE 4), and then incubated for 5 hours. At 0, 3, and 5 hours, samples were assayed for capacitation and motility parameters according to the chlortetracycline (CTC) fluorescent pattern B and computer-assisted sperm analysis, respectively. A higher percentage of CTC pattern B sperm relative to heparin controls was observed at 0 and 3 hours when sperm were incubated with vinpocetine. After 5 hours, the percentage of heparin- and vinpocetine-treated sperm showing pattern B did not differ (P >.05). Rolipram did not affect CTC patterns (P >.05; n = 4). Vinpocetine and heparin both reduced the percentage of progressively motile sperm after 3 and 5 hours, but vinpocetine reduced it more than heparin (P <.05; n = 4). Rolipram transiently increased linearity versus sperm with heparin (P <.05; n = 4). To further test the hypothesis that PDE 1 inhibition permits capacitation, we conducted in vitro fertilization. Vinpocetine did not support the ability of sperm to penetrate homologous oocytes (n = 5). Although cAMP regulation by PDE 1 may occur early during capacitation, downstream events appear to prevent full capacitation from occurring prematurely.
Fournier
Valérie
V
Département des sciences animales, Université Laval, Québec, Québec Canada.
Leclerc
Pierre
P
Cormier
Nathaly
N
Bailey
Janice L
JL
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000502:physiology*; D000814:Aniline Compounds; D000818:Animals; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics; D002417:Cattle; D002751:Chlortetracycline / Q000493:pharmacokinetics; D054677:Cyclic Nucleotide Phosphodiesterases, Type 1; D004801:Eosine Yellowish-(YS); D005260:Female; D005307:Fertilization in Vitro; D005456:Fluorescent Dyes; D007527:Isoenzymes / Q000502:physiology; D008297:Male; D013075:Sperm Capacitation / Q000502:physiology*; D013194:Staining and Labeling
D000814:Aniline Compounds; D000900:Anti-Bacterial Agents; D005456:Fluorescent Dyes; D007527:Isoenzymes; C002712:nigrosin; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054677:Cyclic Nucleotide Phosphodiesterases, Type 1; D004801:Eosine Yellowish-(YS); D002751:Chlortetracycline