Gonadotropin-Releasing Hormone Increases Ability of the Spermatozoa to Bind to the Human Zona Pellucida1

Abstract

Sperm-zona pellucida binding, a crucial step in the process of fertilization, takes place in vivo in the upper portion of the fallopian tube. The presence of GnRH-like peptides in the female and the male genital tract has been described. In this work, the effect of GnRH and related peptides upon sperm-zona pellucida binding ability was studied. Sperm aliquots, capacitated for 4.5 h, were incubated for 5 min with saline (control) or 20 nM of GnRH, C-terminal (1-5) or N-terminal (5-10) fragments of GnRH, Substance P, dynorphin, bombesin, or mixed GnRH (a synthetic peptide with the same amino acids as GnRH but in different order). Sperm were also incubated with the GnRH antagonist Ac-3,4-dehydro-Pro1, -p-fluoro-<FONT SIZE=-1>D-Phe2, <FONT SIZE=-1>D-Trp3,6-LHRH, alone or before adding GnRH. The sperm were then tested using the hemizona assay. After 10 min, the number of zona-bound sperm was determined. In addition, the effect of GnRH upon the acrosome reactions, sperm movement characteristics, and sperm-zona collisions was evaluated. Sperm treated with GnRH bound in higher numbers to the zona than did control sperm (p < 0.005). The GnRH fragments, the GnRH antagonist, and related peptides did not have any effect on sperm-zona interaction; however, the GnRH antagonist totally blocked the stimulatory effect of GnRH. GnRH did not affect the percentage of acrosome-reacted sperm, pattern of sperm movement, or frequency of sperm-zona collisions. I suggest that the increased ability of the sperm to bind to the zona may be due to exposure and/or change of affinity of zona receptors on the sperm plasma membrane.

Gonadotropin-inhibitory hormone (GnIH) receptor gene is expressed in the chicken ovary: potential role of GnIH in follicular maturation

“…Other hormones affecting reproduction, such as GnRH and kisspeptin, have been found to exert a direct effect in the ovaries of several mammalian species by activating their cognate receptors. For instance, GnRH and its receptor are expressed in granulosa cells of developing follicles in the rat ovary (Whitelaw et al 1995) and may play an important role in oocyte maturation (Dekel & Shalgi 1987), follicular atresia or selection (Whitelaw et al 1995), and fertilization processes (Morales 1998). G-protein coupled receptor (GPR)54, a receptor for kisspeptin, has been found to be expressed in the human testis (Kotani et al 2001) and rat ovary (Castellano et al 2006).…”

Gonadotropin-Releasing Hormone-Stimulated Sperm Binding to the Human Zona Is Mediated by a Calcium Influx1

“…These findings suggest that GnRH-like molecules may play either or both an endocrine or paracrine function in these extrapituitary tissues [35]. In accord with this, it was shown that GnRH and GnRH agonists enhanced bovine in vitro fertilization through an effect on the cumulus-oocyte complex [36] and that GnRH increased sperm binding to the human ZP by a direct effect on the sperm cells [37]. Moreover, we have shown that GnRH antagonists inhibited sperm-ZP binding in humans in a dose dependent manner [38].…”

“…As a result of freezing and thawing, these oocytes were never viable. Before use, the oocytes were cut to obtain two equal halves, or hemizonae [37,38,40,42,43].…”

Potential role of gonadotrophin-releasing hormone (GnRH)-I and GnRH-II in the ovary and ovarian cancer.

“…GnRH and GnRH agonists have been shown to increase the cleavage rate of bovine oocytes (Funston & Seidel 1995). Moreover, GnRH enhanced sperm-zona pellucida binding ability, which is completely blocked by cotreatment with GnRH antagonist (Morales 1998). During the luteal phase, but not the follicular phase of the menstrual cycle, both GnRH mRNA and protein have been demonstrated in the human Fallopian tube, where spermatozoa and oocytes are deposited to form zygotes (Casan et al 2000).…”