Enlarge image
Couple (symbol image): There are millions of sperm in one ejaculate
Photo: Tara Moore/Getty Images
Statistically speaking, anyone who wants to prevent pregnancy does not have such a bad hand: the probability that a specific sperm will fertilize an egg cell is one in 500 million, the chances of winning the lottery are better.
Why are babies born anyway?
There's just so much sperm.
About 20 to 60 million sperm cells leave the male body per effusion.
An international research team has now developed a way that could probably turn off every single sperm.
The study raises hopes for a new contraceptive, because so far the repertoire for men - apart from condoms - is manageable.
Hormonal contraceptive methods, for example, target the female body by preventing ovulation, among other things.
Hormone injections for men, on the other hand, failed more than ten years ago because of side effects such as mood swings, headaches or loss of libido.
The possible form of contraception, which researchers from the USA and Belgium are now presenting in the specialist journal PNAS, does not require any hormones at all.
The principle: A sperm has to change its surface tension before it can penetrate an egg cell.
To do this, it pumps potassium ions out of the cell via a channel.
In technical jargon, this is called hyperpolarization.
This process takes place in the so-called SLO3 channel.
The researchers have now found a substance that can block it.
The sperm can then no longer penetrate an egg cell, their mobility would also be inhibited and they become infertile.
That's the theory.
"Drugs based on the SLO-3 inhibitor could prevent human sperm from fertilizing egg cells," write the study authors, led by Celia Santi of the Washington University School of Medicine.
And not only that. The discovery could also explain why some men in whom the SLO-3 channel is altered are infertile.
There is still a long way to go before the finished contraceptive is produced
"Mutations in the channel that impair its function could be a reason for previously unexplained cases of male infertility," says Artur Mayerhofer from the Biomedical Center Munich, the Science Media Center, who was not involved in the study.
The potential of a new contraceptive is clearly there.
However, he outlines a long way to get there:
So far, the study results are based on experiments in the laboratory.
Whether the blocked sperm are also infertile in real life must be shown in further studies in animals and humans.
Then it would have to be proven that the substance is well tolerated.
Ultimately, the question of how high the level of contraceptive safety really is is also crucial.
"There is still a long way to go, but it could be worth it," says Mayerhofer.
There is a need for new contraceptive methods that interfere as little as possible with the bodies of women and men.
The pill in particular can lead to side effects and is becoming increasingly unpopular with women.
At least as far as compatibility is concerned, there is reason for optimism.
Because, according to everything that doctors know, the SLO3 channels only occur in sperm and in no other body cell.
Should a contraceptive actually be developed from these findings, the application would still probably get stuck with women again.
Mayerhofer considers vaginal application as a gel to be the most likely.
koe