Ovulation-inducing factor in semen: Implications for mammalian fertility

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We have discovered a component in the semen of the male that elicits an ovulatory response in the female, and we have found it in every species examined thus far. The existence of an ovulation-inducing factor (OIF) in seminal plasma has broad implications and immediately evokes questions about identity, tissue sources, mechanism of action, role among species, and clinical relevance in infertility. Most of these questions remain unanswered. Ovulation in mammals may be classified as induced (elicited by mating) or spontaneous (elicited by natural hormonal rhythm). However, a continuum exists and some mechanisms are common to both. In a series of pioneering studies, we have documented that OIF exists in the semen of males and influences ovarian function in females of both spontaneous and induced ovulators, OIF in seminal plasma induces ovulation via an endocrine route (through the blood stream) in the female, and has a dose-dependent effect at doses as small as that present in 1/100th of an ejaculate. Most recently, we discovered that OIF in seminal fluid is identical to nerve growth factor (NGF) - a factor previously associated with promoting growth and development of nerves. Importantly, it is present in greater quantities in seminal plasma than in any other body fluid. The long-term objective of our research program is to shed new light on mechanisms controlling ovulation among mammalian species. Short-term objectives are focused on the role of seminal OIF in ovulation by determining 1) the site of action in the female (brain, pituitary, ovary), 2) the source of OIF within the male reproductive tissues, 3) the relationship between OIF in semen and male fertility, 4) the effects of OIF on the corpus luteum (in support of pregnancy), and 5) the relative role of OIF vs other copulatory stimuli on ovarian function in the female. We are at the forefront of research on OIF and on the cusp of a shift in our understanding of how the male influences the ovaries of the female. Uncovering the biological role of OIF in semen will have an important impact on diagnosis of male and female infertility, and on the development of new treatments for infertility and contraception.