Unisex contraceptives

Contraceptive used both men women might one day available. Scientists in US have discovered sperm are starved calcium become sluggish, swim well, unable penetrate an egg. They believe discovery may lead to the development of hormone-free pill that can be taken a man or woman before sex and will work by blocking calcium.

The team, from the Harvard Medical School in Boston, stumbled on the discovery while looking for genes controlling the flow of calcium ions in mice. One was found only in the testes. When it was 'switched off', there was a substantial effect on the fertility of the mice.

The gene codes for a protein called CatSper, and is expressed only in the tails of sperm. When the gene had been switched off, it was found that sperm were unable to use their tails in a whiplash motion, causing them to swim more slowly and have less power.

The scientists have not discovered whether the gene directly controls the flow of calcium but it is believed that any pill that targeted the calcium in sperm tails would make an efficient contraceptive. It is thought that it would also work for women as it would affect sperm in their reproductive system. Such a pill would have many benefits to hormone-based oral contraceptives taken daily by women. It is expected that there would be less side-effects, for example. Pharmaceutical companies are said to be very interested, and it is hoped that human trials might begin within five years. The discovery may also lead to more research and treatments for male infertility.