The researchers studied how nitric oxide affects hamster sperm function by using specific inhibitors of nitric oxide synthase. They found that one inhibitor affected sperm motility, hyperactivation, and acrosome reaction, while the other only affected hyperactivation and acrosome reaction. Both inhibitors were able to prevent sperm capacitation by changing protein tyrosine phosphorylation. However, they did not affect protein serine phosphorylation. This shows that nitric oxide is necessary for sperm capacitation.