Sperm can not smell

Fragrances play no role for sperm

28/02/2012

Sperm are directed by certain attractants on their way to the egg cell, but smelling has nothing to do with it. The so-called „Lily of the Valley phenomenon“, According to the results of a research team of the Bonn-based foundation Caesare and the Forschungszentrum Jülich, fragrances influence the journey of the sperm, based on a laboratory phenomenon.

The previous assumption that sperm are led on their way to the egg cell of fragrances, is refuted. Researchers at the Caesar Foundation (Center for Advanced European Studies and Research) in Bonn, together with researchers from Forschungszentrum Jülich, have discovered that the spermatozoa have no olfactory signaling pathway but are guided by a hormonal attractant - progesterone.

Lily of the Valley phenomenon just a laboratory phenomenon
The so-called „Lily of the Valley phenomenon“ For a long time, it has been considered a relatively accepted theory for the control of sperm on their way to the egg. German and American scientists had in 2003 in the journal „Science“ published a study, according to which a part of the lily of the valley scent lures the sperm towards the egg. However, the Bonn scientists Caesare Foundation (associated with the Max Planck Society) did not want to follow this theory. Especially so far, neither lily of the valley fragrance nor any other „Perfume found in the female genital tract“ who supports this theory Timo Strünker from the Department of Molecular Neurosensors at the Caesare Foundation told the news agency „dpa“. Last year, the Caesare researchers presented an alternative model, according to which the hormone progesterone as a chemical guide directs the sperm towards the oocyte. Now the researchers, together with scientists from Forschungszentrum Jülich, have shown that the lily of the valley fragrance has a similar effect on the sperm as progesterone, but this can only be achieved in the laboratory, because it requires a concentration 1000 times higher than that of the hormone. The „Lily of the Valley phenomenon“ based on accordingly „on a laboratory artifact“, there is no olfactory signaling pathway in spermatozoa, the scientists report.

Sperm controlled by chemical attractants
Previous studies have already shown that oocytes help sperm in their path by releasing certain attractants that affect the sperm's swimming motion ... The theory that perfumes serve as a guide to sperm was modeled on a control through the female sex hormone progesterone. Now the researchers have around Dr. Timo Strünker demonstrated that the effect of progesterone on the so-called „CatSper ion channels (cation channels of sperm)“ responsible for the control of sperm. Although show the lily of the valley scent „bourgeonal“ a comparable effect on the „CatSper ion channels“ like progesterone, but the fragrance in the female genital tract does not occur and act only from a 1,000-fold higher concentration than progesterone, according to the latest results of the researchers. Calcium can flow into the sperm via the CatSper channels, which are exclusively in spermatozoa, whereupon they adjust their swimming direction. Men who have CatSper channel dysfunction due to a genetic defect are infertile.

Pill for the man?
Since the lily of the valley fragrance is not found in the female genital tract and can only be achieved in an overdose comparable effect as with progesterone, that is „Lily of the Valley phenomenon“ according to the Caesare researchers only a laboratory phenomenon. „Sperm does not work like olfactory cells in the nose“, emphasized study leader Dr. Timo Strünker opposite the news agency „dpa“. Instead, the sperm take over the CatSper channels „the chemical environment in the fallopian tube“ true and can „so track down the egg“, the neuroscientists report. Thus, the spermatozoa use the CatSper channels on their arduous journey to the egg cell to keep coming up with different ones „chemical guide“to orient. However, it has not yet been clarified why the sperm react so seldom to different substances such as lily of the valley or menthol. The scientists now want to focus in upcoming studies on identifying further attractants in the fallopian tube, which determine the control of sperm in addition to progesterone. According to the Caesare researchers, the findings are as well „also medically significant“, because they could enable the development of novel contraceptives (pill for men), „if it were possible to interfere with the effect of female factors on the CatSper channels.“ (Fp)

Image: Thommy Weiss