Mating effects on female reproductive organs: the paradigm of estrogen signaling pathways in the oviduct

Abstract

Mating induces several physiological changes in the female reproductive tract independently of oocyte fertilization, which are potentially required for a successful pregnancy. These effects include modifications in the cellular and molecular mechanisms by which some steroidal hormones exert their actions in the oviduct and uterus, changes in the expression of some key molecules inside the uterus and modulation of the steroidogenic functions in the ovary. Mating impinges on the female reproductive tract with sensory stimulation, seminal fluid and sperm cells, so these effects may involve a direct interaction between the cells of the female reproductive tract and the different components of the seminal plasma and/or spermatozoa to modulate the immune system or neuroendocrine changes elucidated by the mechanical stimulation of the cervix, which indirectly affect the functioning of the cells that compose the female reproductive tract. In this chapter we will review the available literature on the effects of mating in the physiology of oviduct, ovary and uterus highlighting a hitherto unsuspected early, strong and broad influence of mating on the physiology of female reproductive organs. We will be specially centered into review of the well-defined effect of mating on the rat oviduct, where it changes the mechanism by which estradiol accelerates oviductal egg transport, from a nongenomic to a genomic pathway. This change has been named intracellular pathway shifting (IPS) and reflects a novel example of functional plasticity in well-differentiated cells induced by mating. We will describe that IPS involves inhibition of the conversion of estradiol to 2-methoxyestradiol, which probably protects the embryos from the deleterious effect that methoxyestradiols exert during the embryo development. IPS seems to involve changes in intraoviductal signaling mediated by cytokines TNF-a and TGFb and is independently induced either by cervico-vaginal stimulation with a rod glass or by intrauterine insemination. Such redundancy of triggering factors suggest that IPS is an important element in the reproductive strategy.