Sperm transport and retention at the fertilization site is orchestrated by a chemical guidance and oviduct movement

Abstract

In mammals, only a few spermatozoa arrive at the fertilization site. During the last step in the journey to the egg, apart from their selfpropulsion, spermatozoa may be assisted by oviduct movement and/or a guidance mechanism. The proportion of rabbit spermatozoa that arrive at the fertilization site was determined under in vivo conditions, in which either the ovulation products (secreting chemoattractants) and/or the oviduct movement (causing the displacement of the oviductal fluid) was inhibited. When only one of these components was inhibited, sperm transport to the fertilization site was partially reduced. However, when both the ovulation products and the oviduct movement were inhibited, almost no spermatozoa arrived at the fertilization site. The results suggest that spermatozoa are transported to and retained at the fertilization site by the combined action of a chemical guidance and the oviduct movement. A working model is proposed to explain how these two mechanisms may operate to transport spermatozoa to the fertilization site, probably as an evolutionary adaptation to maximize the chance of fertilizing an egg.

Live Birth from Slow-Frozen Rabbit Oocytes after In Vivo Fertilisation

“…Thus, the entrance to the infundibulum was not accessible via laparoscopy as a consequence of the surgery in ovariectomised females, whereby oviduct ligation induced an accumulation of tubal fluid. This accumulation of tubal fluid after oviduct ligation has been described previously [54].…”

Natriuretic peptide type C induces sperm attraction for fertilization in mouse

“…Experimental data suggest chemical attraction for spermatozoa near the oocyte in the ampulla, to trigger fertilization15. The signal originates in the oocyte microenvironment1617, including follicular fluid181920, oviductal fluid19 and oocyte-conditioned media21, which is most likely conducive to capacitated spermatozoa2223 and is correlated with fertilization success24.…”

Distribution of thyroid hormone and thyrotropin receptors in reproductive tissues of adult female rabbits

“…The presence of these receptors in the different tissue layers of the oviduct suggests that thyroid hormones and TSH are involved in the fertilization process. In this regard, secretions and the ciliary movement of the oviductal epithelium are relevant for the sperm storage and capacitation, the oocyte maturation and fertilization, as well as for the sperm, oocyte, and zygote transport (37)(38). The contraction of the smooth musculature and mesotubarium muscle promotes the transport of gametes and ova along the oviduct (38)(39).…”

“…In this regard, secretions and the ciliary movement of the oviductal epithelium are relevant for the sperm storage and capacitation, the oocyte maturation and fertilization, as well as for the sperm, oocyte, and zygote transport (37)(38). The contraction of the smooth musculature and mesotubarium muscle promotes the transport of gametes and ova along the oviduct (38)(39). Moreover, hypothyroidism increases the size of the oviductal epithelium in rabbits, which could be related to changes in the activity of these cells (10), and affects the smooth musculature in rats (6).…”