Effect of norethisterone and its A-ring reduced metabolites on the acrosome reaction in porcine spermatozoa

Abstract

The synthetic progestin, norethisterone (NET), has been reported as a contragestational postcoital agent in humans, rodents and rabbits. The effect and molecular mechanisms of NET and its A-ring reduced metabolites, 5alpha-NET and 3beta5alpha-NET, on the acrosome reaction (AR) are unknown. The aim of this study was to assess the effect of these compounds on an in vitro progesterone-induced AR in porcine spermatozoa. The spermatozoa were obtained from semen ejaculated by proven fertile adult pigs. Seminal plasma removed and incubated under capacitating conditions was performed in TALP-Hepes medium for 4 h. Progesterone (P4) and three different progestins: norethisterone (NET), 5alpha-norethisterone (5alpha-NET) and 3beta5alpha-NET were then added at equimolar doses, and the spermatozoa were incubated for 15 min. Double-staining with PSA-FITC and Hoechst-33258 assessed the AR and sperm viability. Both P4 and NET induced the AR, while 5alpha-NET not only did not induce this process, but was able to block the effect of P4 on the spermatozoa. 3beta5alpha-NET was not able to inhibit P4 action. These results suggest that NET and its A-ring reduced metabolites act in different ways on the progesterone-induced AR in porcine spermatozoa.

Inhibition of the acrosome reaction (AR) and fertilization capacity of mouse spermatozoa by norethisterone A-ring reduced metabolite (5alpha-NET)

“…Our hormone binding experiments have shown that neither NET nor 5 α ‐NET are able to displace the binding to progesterone receptor (data no shown). This suggests that the effects observed in this study and in porcine spermatozoa (Martínez et al. , 2002) might have occurred through pathways different than that of the membrane progesterone receptor.…”

“…In a previous study, we demonstrated the agonistic effect of norethisterone (NET) and the antagonistic effect of its A‐ring reduced metabolite 5 α ‐NET on the pig spermatozoa AR (Martínez et al. , 2002).…”

“…Recently, Kamischke et al. (2000, 2002) demonstrated that norethisterone enanthate (NETE) in combination with testosterone undecanoate ester (TU) suppressed spermatogenesis in humans, and our group showed a direct effect of NET and its A‐ring reduced metabolites in the acrosome reaction (AR) in pig spermatozoa (Martínez et al. , 2002).…”