NEUROTENSIN STIMULATES THE SPERM ACROSOME REACTION AND REDUCES PERCENTAGES OF FERTILIZATION IN VITRO

Abstract Objective To determine the impact of neurotensin (NTS), a naturally occurring peptide, on the function of human and non-human primate sperm. Design Experimental Study. Setting University-based research laboratory. Patients/Animals Consenting normozoospermic human donors; cynomolgus macaques. Intervention(s) None. Main Outcome Measure(s) Sperm acrosome status was assessed. Computer assisted semen analysis (CASA) assessed sperm motility, progression, and velocity. Immunocytochemistry and receptor selective agonists were used to identify specific NTS receptors on sperm. Monkey oocytes were obtained after ovarian stimulation, and NTS-treated monkey sperm were used for in vitro fertilization (IVF). Results NTS treatment of human sperm stimulated the acrosome reaction in both a dose-dependent (0.1-10 μM) and time-dependent (5-30 min) manner. NTS treatment did not alter sperm motility or progression. Both a general NTS receptor antagonist (SR142948) and a NTSR1 selective antagonist (SR48692) reduced the ability of NTS to stimulate the acrosome reaction. NTSR1, but not NTSR2 or SORT1, was detected in monkey sperm by immunostaining. NTS treatment also compromised the ability of sperm to fertilize an oocyte. Percentage of fertilization with untreated monkey sperm and monkey oocytes was 72%. Sperm pre-treated with NTS yielded a significantly lower fertilization rate of 18%. Conclusion NTS effectively stimulates the acrosome reaction in human and monkey sperm. NTS produced by the oviduct or cumulus cells may promote natural fertilization. Pre-treatment of sperm with NTS significantly reduces fertilization. Exposure of sperm to NTS prior to reaching the oviduct has potential for contraceptive development. Identification of NTSR1 as the mediator of NTS action provides a specific target for future studies.