THE protein that stops sperm 鈥渇iring鈥� before it meets a woman鈥檚 egg has been
found by Dutch researchers. It may partly explain why some in vitro
fertilisation techniques have a low success rate.
Before a sperm cell is able to fertilise an egg, it must chew through the
egg鈥檚 casing with the help of an enzyme called acrosin. Joost Meijers and his
colleagues at the University of Utrecht showed that the heads of human sperm are
coated with a protein called protein C inhibitor (PCI). They found that this
blocks the activation of acrosin and stops the sperm releasing its load
prematurely.
In the current issue of the journal Biology of Reproduction (vol 58,
p 670) the researchers say other factors in semen strip sperm of PCI on
ejaculation. Meijers鈥檚 team speculates that sperm taken from the epididymis,
where sperm are stored before mixing with semen, may have low fertility and
could be unsuitable for use in IVF.
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