P-56: The Effect of Hydrostatic Pressure on Mouse Sperm Hyperactivation

Background: Mammalian sperm are not ready to fertilize oocyte immediately after ejaculation. Sperm achieve this ability after undergoing the processes of capacitation and hyperactivation. Hyperactivation refers to a change in the motility pattern of the sperm. Pharmacological reagents and physical-mechanical forces have been used in sperm from a variety of species. Hydrostatic pressure is a crucial component of cell environment and fundamental physical quantity; also it is the main factor of both integrity and function of cells. Sperms exposed to different range of hydrostatic pressure within male and female reproductive system. Previous studies demonstrated that hydrostatic pressure can change the sperm motility. This study examined the effect of exposing mouse sperm to hydrostatic pressure to induce hyperactivation. Materials and Methods: Sexually mature NMRI male mice, age of 8-12 weeks-old were as sperm donors. Sperms separated from the caudal epididymis and maintained in T6 culture medium supplemented with 10% BSA and divided into five treatments. The sperm suspension of treatments I, II, III and IV were subjected to hydrostatic pressure(5, 10, 25 and 50 mmHg; respectively) for 30, 60 and 120 minutes. In treatment V sperm suspension was transferred to similar pressure chamber without hydrostatic pressure exposure. After depressurization, the sperm suspension removed from the pressure chamber and sperm viability and motility were evaluated. Results: Our results showed that sperm viability decreased in treatments III and IV compared to treatments I, II and V after 60 and 120 minutes (p<0.05). The percentage of hyperactivated sperms increased in treatment I and II compared to treatments III , IV and V after 60 and 120 minutes (p<0.05). The percentage of hyperactivated sperms decreased in treatments III and IV compared to treatments I, II, and V, after 120 and 30, 60 and 120 minutes; respectively (p<0.05). Conclusion: Hydrostatic pressure affects sperm viability‌ and motility in a dose and time manner. Hydrostatic pressure as a mechanical force can be use to induce sperm hyperactivation.