Insemination extender supplementation with bestatin and EDTA has no effect on rabbit reproductive performance

Abstract

The addition of aminopeptidase inhibitors (AMIs) to rabbit semen extenders could be a solution to decrease the hormone degradation (GnRH) by the aminopeptidases existing in the seminal plasma. Therefore, the quantity of GnRH needed to induce ovulation in doe would be comparable with the amount administered intramuscularly (i.m.). This study was conducted to evaluate the effects of two AMIs (bestatin and EDTA) on rabbit semen quality parameters, β nerve growth factor (β-NGF) degradation and reproductive performance after artificial insemination. Results showed that seminal quality was not affected by the incubation with AMIs; the values of motility, acrosome integrity and sperm viability were not significantly different between the AMIs and the control groups (positive i.m. and negative intravaginally without AMIs). In addition, the aminopeptidase activity of seminal plasma was inhibited in a 55.5% by the AMIs as well as β-NGF degradation. On the other hand, regarding the effect of AMIs on reproductive performance, our results showed that the presence of bestatin and EDTA did neither affect fertility (85.3 vs. 88.6%), nor the prolificacy rate (10.12 vs. 10.51 kits per delivery), comparing AMIs group to positive control group, respectively. We conclude that the addition of specific AMIs in the rabbit semen extender has no effect on reproductive performance. Therefore, due to the fact that AMIs inhibit part of the aminopeptidase activity that degrades the GnRH analogue and β-NGF, they could be used to develop new extenders with less hormone concentration.

Characterization of β-Nerve Growth Factor-TrkA system in male reproductive tract of rabbit and the relationship between β-NGF and testosterone levels with seminal quality during sexual maturation

“…Moreover, reports in humans have found that the b-NGF/TrkA system exerts effects on semen parameters [47,48]. b-NGF levels observed in the SP were similar to those reported in rabbits [9,49] but b-NGF concentration in BP was higher than those described by Maranesi et al [9]. Differences among studies may be explained in terms of different kits and laboratory techniques used.…”

Recombinant rabbit beta nerve growth factor production and its biological effects on sperm and ovulation in rabbits

“…However, in more recent studies this neuropeptide has been also identified as an ovulation-inducing factor (OIF) present in the seminal plasma (SP) of some reflex ovulating species such as camelids or rabbits [2–5]. In rabbits, the neuropeptide and its receptors (TrkA and p75) have been identified in all male and female reproductive tissues (testes, epididymis and accessory glands [6–10], SP [7, 8, 10, 11], uterus, oviduct and ovary [12–14]). While some studies have suggested a role of β-NGF in the mechanism of ovulation in rabbits [8, 12, 15], evidence of its role as an OIF in this species, as found in camelids, is still scarce.…”

Protection of GnRH analogue by chitosan-dextran sulfate nanoparticles for intravaginal application in rabbit artificial insemination

“…However, due to degradation by aminopeptidases and the low absorption in the vagina mucosa, there is a decrease in the analogues' bioavailability and large doses are required for ovulation induction following vaginal administration. According to a previous work [6], the employment of bestatin and EDTA in the rabbit insemination extenders inhibited part of the seminal aminopeptidase activity without affecting reproductive performance. On the other hand, we have developed CS-DS nanoparticles to entrap the GnRH analogue and a previous in vitro characterization showed that these nanoparticles did not affect rabbit seminal quality [12].…”

“…CS and DS were dissolved (0.05%) in the Control medium, which consisted in Tris-citric acid-glucose (TCG) supplemented with bestatin 10 µM and EDTA 20 mM [6].…”

“…In previous works, we have proved that rabbit's seminal plasma aminopeptidase activity affects the bioavailability of GnRH analogues added to the insemination extenders [4]. As a consequence, we have been trying to develop new extenders supplemented with protease and aminopeptidase inhibitors in order to protect the hormone from being degraded without affecting reproductive Accepted manuscript, doi:10.1016/j.theriogenology.2018.05.008 performance [5,6]. We have observed that extender supplementation with aminopeptidase inhibitors (AMIs) as bestatin and EDTA did not affect rabbit seminal quality nor reproductive performance [6], but inhibited part of the seminal plasma aminopeptidase activity.…”