A study published in the August 20 edition of the Proceedings of the National Academy of Sciences (PNAS) reveals that an international team of scientists at Saskatchewan University discovered a protein in semen, which influences the female brain to prompt ovulation and that this molecule also regulates the growth, maintenance, and survival of nerve cells. The accessory sex glands in male mammals contribute seminal fluid to semen, yet so far there is little knowledge about the fluid’s role and that of the glands that produce it.
Leading researcher Greg Adams, a professor of veterinary biomedical sciences at the Western College of Veterinary Medicine at Saskatchewan University says: “From the results of our research, we now know that these glands produce large amounts of a protein that has a direct effect on the female.”
The study raises some interesting questions regarding fertility in mammals and humans. The researchers have found that the protein, which they call ovulation-inducing factor (OIF), is present in all species of mammals that they have investigated so far. They compared OIF to thousands of other proteins, such as the nerve growth factor (NGF) that primarily occurs in the body’s nerve cells and Adams says: “To our surprise, it turns out they are the same molecule. Even more surprising is that the effects of NGF in the female were not recognized earlier, since it’s so abundant in seminal plasma.”
Even though OIF/NGF may work differently in each individual animal, the researchers found that it is present in all mammals they have studied, ranging from llamas, cattle and koalas to pigs, rabbits, mice and humans, which suggests that it plays a significant part in all mammal’s reproduction. This raises questions about its role in various species, how it works and its clinical significance to human infertility amongst other questions.
OIF/NGF in the semen functions as a hormonal signal that works through the hypothalamus of the female brain and the pituitary gland, which in turn triggers the release of other hormones that signal the ovaries to release one or several eggs depending on the species. The team focused on llamas and cattle in their study and found that llamas are “induced ovulators,” which means they only ovulate when inseminated in contrast to cows as well as humans that are “spontaneous ovulators,” which means the release of an egg is stimulated by a regular buildup of hormones.
The team compared OIF and NGF with various techniques and discovered that they are the same size and cause the same effects across species. The structure of the molecule was confirmed at the Canadian Light Source synchrotron at Saskatchewan University.
“The idea that a substance in mammalian semen has a direct effect on the female brain is a new one. This latest finding broadens our understanding of the mechanisms that regulate ovulation and raises some intriguing questions about fertility.”