A team of researchers has identified a chemical signal responsible for inducing ovulation in mammals.

Gregg Adams of the University of Saskatchewan, along with a team of researchers, have identified a compound present in the semen of male mammals which acts as a hormone stimulating the release of egg cells in females. “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,” says Adams.

The study was conducted on llamas and cattle, and could indicate a wider pattern of physiological activity in most mammals. The study is reported by the University of Saskatchewan.

Females of many mammalian species, including cattle and humans, ovulate spontaneously in response to changing physiological and hormonal conditions in the body. Other species, such as llamas, ovulate only in response to insemination. In this study, the team identified the factor responsible for stimulating ovulation in llamas, and discovered that it was identical with the previously known nerve growth factor (NGF) compounds. “To our surprise, it turns out they are the same molecule,” said Professor Adams. “Even more surprising is that the effects of NGF in the female were not recognized earlier, since it’s so abundant in seminal plasma.”

When llama NGF was applied to cattle, which ovulate without insemination, the team discovered that the length of the ovulation cycles were shortened. This indicates that even in species where ovulation is spontaneous, NGF can still act to stimulate it.

Adams says, “This latest finding broadens our understanding of the mechanisms that regulate ovulation and raises some intriguing questions about fertility.”

While NGF is already known to have local effects in the ovaries where it is produced, Adams believes that this study indicates that it also is carried in the bloodstream to the brain where it affects the overall regulation so the hormones that control ovulation in females. Although Adams notes that human females do not require NGF in order to ovulate, he also says that the discovery that it plays a role in regulating ovulation could potentially lead to new understanding of some forms of human infertility.

The research is published in the Proceedings of the National Academy of Sciences.