male contraceptives? New substance can paralyze sperm

NAt least from a physical point of view, contraception is always a woman’s job. Almost all established contraceptives – whether birth control pills, spirals or diaphragms – start on the female body. Men can only use condoms to prevent pregnancy.

Johanna Kuroczik

Editor in the “Science” department of the Frankfurter Allgemeine Sunday newspaper.

However, researchers are now presenting a substance in “PNAS” that paralyzes sperm – and would thus be a possible approach for a new type of contraceptive for men.

The substance starts directly during the fertilization process: In order to be able to fuse with an egg cell, the sperm has to change its surface tension. This process is called hyperpolarization. The sperm transports massive amounts of potassium ions out of the cell interior. A potassium channel plays the decisive role here, SLO3. This only occurs in sperm.

And this is where the substance VU0546110 developed by the scientists from Belgium and the USA works: it blocks the potassium channel. Thus, hyperpolarization would not be possible, the sperm could not fuse with the ovum. In addition, the sperm would be prevented from moving, the sperm would be paralyzed and the ovum would not be fertilized.

“This means there is a chance of finding new membrane-based targets for male contraception,” says Stefan Schlatt, who heads the Center for Reproductive Medicine and Andrology at the University of Münster, to the Science Media Center. “Since sperm are very simply built and there are only a few channels in their membranes, which are often sperm-specific, it seems possible to find highly selective substances here that can prevent fertilization, but otherwise have little or no cellular side effects.”

The substance works without hormones

An advantage would be that this principle does not interfere with the hormone balance. For a long time, research was carried out on a kind of pill for men. However, a very advanced study was discontinued more than ten years ago and the approach discarded. The tried and tested remedy should basically work just like the birth control pill, which intervenes in the female hormone balance and thus prevents ovulation. In men, artificial progestin and testosterone in the brain should ensure that certain sex hormones are no longer produced, which prevents sperm production in the testicles.

This was also effective in studies, but the research was stopped because some men developed side effects, such as severe depressive symptoms. A problematic double standard, experts found, since the birth control pill is also known to have unpleasant effects in women, such as nausea or depression.

The new substance VU0546110 would not affect the hormone balance. However, this is only theory so far – because the road to an actual drug, whether as a gel or tablet, would still be very long and full of challenges. So far, these are only laboratory tests. The substance would therefore still have to be tested on animals and finally in extensive studies on humans to ensure safety and efficiency.

“The laboratory tests are complex and they were carried out on relatively few human sperm, as I can gather from the work,” says cell biologist Artur Mayerhofer, who, among other things, heads a working group at the Biomedical Center in Munich and conducts research on male infertility. “If they can be confirmed, the results of the study will have significance for the diagnosis of male infertility: mutations in the channel that impair its function could be a reason for previously unexplained cases of male infertility.”

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