Can permeable super oxide dismutase mimetic agents improve the quality of frozen–thawed ram semen?

This study was carried out to assess the effects of MnTBAP, a cell permeable antioxidant, on motility, membrane integrity, capacitation status and in vitro fertilization ability of frozen-thawed ram semen. Fresh semen ejaculates were collected with artificial vagina from five rams, mixed and divided into five equal fractions, and diluted (1:20v/v) with commercial extender, Bioxell®, containing 0 (control), 50, 100, 150 and 200μM of MnTBAP. All diluted sperm suspensions were cooled to 5°C for 2h followed by transfer into 0.5ml French straws before being stored in liquid nitrogen. The results showed that MnTBAP supplementation of extender improved ram semen quality in a dose-dependent manner. Accordingly, the extender supplemented with 150μM MnTBAP resulted in higher sperm motility and improved acrosomal membrane integrity compared to control. However, further supplementation (200μM) with MnTBAP not only did not improve the results but inversely affected motility and membrane integrity. The results of in vitro fertilization (IVF) indicated that the presence of MnTBAP in semen extender has a marginal beneficial effect on developmental competence of inseminated oocytes, though this improvement was not significant. In conclusion, this study demonstrated that semen extender supplemented with MnTBAP can reduce the oxidative stress provoked by freeze/thaw processes. Moreover, beneficial effect of 100μM of MnTBAP on preservation of spermatozoa in a non-capacitated state post freezing, an important criterion for in vitro or in vivo fertilization, was observed. However, at 150μM of MnTBAP, the harmful effects of cryopreservation on membrane integrity were decreased. Regarding to importance of non-capacitated spermatozoa during IVF or artificial insemination, the optimum MnTBAP concentration appears to be 100μM for commercial ram semen extender tested here.