Mol. Hum. Reprod. Advance Access originally published online on July 22, 2005
Molecular Human Reproduction 2005 11(7):523-529; doi:10.1093/molehr/gah188
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Protein tyrosine phosphorylation, hyperactivation and progesterone-induced acrosome reaction are enhanced in IVF media: an effect that is not associated with an increase in protein kinase A activation
1Reproductive Biology and Genetics Group, Division of Medical Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK, 2Assisted Conception Unit, Birmingham Women’s Hospital, Birmingham B15 2TG, UK, 3Centre for Research in Contraceptive and Reproductive Health, Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA, 4Department of Medical Biochemistry and Immunology, Cardiff University, Cardiff, CF14 4XN, UK and 5School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
6 To whom correspondence should be addressed at: Reproductive Biology and Genetics Group, University of Birmingham, Institute of Biomedical Research, Edgbaston, Birmingham, B15 2TT, UK. E-mail: l.lefievre{at}bham.ac.uk
Sperm capacitation is a prerequisite for successful in vitro fertilization (IVF) and therefore a focus of sperm preparation in IVF laboratories. The technology of IVF is, therefore, potentially valuable in advancing our understanding of the molecular processes that occur during sperm capacitation. We have investigated sperm capacitation induced by a commercial IVF medium compared to that occurring in standard capacitating medium (CM) typically used in a nonclinical setting. Percoll-washed spermatozoa were resuspended in Cook® Sydney IVF medium, Cook® Sydney IVF sperm buffer, Earle’s balanced salt medium (capacitating medium) or a modified Earle’s balanced salt medium [non-capacitating medium (NCM)] for up to 120 min at 37ºC and, if applicable, in the presence of 5% CO2 in air. Sperm protein kinase A (PKA) activity, PKA-dependent serine/threonine phosphorylation, tyrosine phosphorylation, hyperactivation and progesterone-induced acrosome reaction were evaluated. IVF medium was shown to accelerate sperm capacitation (compared with capacitating medium) as determined by tyrosine phosphorylation, sperm hyperactivation and progesterone-induced acrosome reaction. This effect was not associated with enhanced activation of PKA or increased levels of serine/threonine phosphorylation. In contrast, IVF sperm buffer (used for sperm preparation) did not stimulate sperm capacitation when incubated for up to 90 min. We have shown that different capacitating media vary strikingly in their efficacy and that this difference reflects activation of a pathway other than the well-characterized activation of soluble adenylyl cyclase/cAMP/PKA.
Key words: acrosome reaction/hyperactivaton/PKA-dependent serine/protein kinase A/threonine phosphorylation/tyrosine phosphorylation
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