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

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.

Acrosome reaction in fertile and subfertile boar sperm

The main purpose of sperm evaluation is to predict its fertilizing ability. However, basic sperm test results show a low correlation with fertilizing ability. The purpose of this study was to determine whether there is an association between acrosome reaction (AR) and the incidence of subfertility of normal sperm boar. The production records of 22 farms were analyzed to identify boars with low fertility and/or prolificity, classified as subfertile. Twenty-two subfertile boar semen samples were analyzed and compared with 51 samples of fertile boars. Sperm were capacitated during 4 h at 39 degrees C. viability was determined by bisbenzimide (Hoechst-33258) staining. Acrosome reaction was assessed with fluorescein isothiocyanate conjugated Pisum sativum agglutinin. The percentage of spontaneous acrosome reaction (SAR) was not significantly different in fertile (4.5%) and subfertile boars (4.75%) (p > .05). Nevertheless, the percentage of progesterone-induced acrosome reaction (IAR) was significantly lower in subfertile boars (5.75%) as compared with fertile boars (10%) (p < .01). These results suggest that assessment of IAR in vitro may be a useful parameter to identify subfertility in boars.

Changes in cyclin B localisation during pig oocyte in vitro maturation

The localisation of cyclin B throughout in vitro maturation of pig oocytes was determined by indirect immunofluorescence using a monoclonal antibody specific for an epitope of the human cyclin B. Maturation of pig oocytes was induced by addition of Pergonal (2 UI/ml of FSH/LH) and beta-oestradiol to the medium where isolated ovarian follicles were cultured for up to 72 h. Immature gametes with an intact germinal vesicle were observed during the first 30 h of culture. Only 10% were competent to reinitiate meiosis and showed germinal vesicle breakdown (GVBD) after 36 h. However, after 48-72 h, 60% of the oocytes accomplished their maturation and showed metaphase chromosomes. Immature oocytes showed cyclin B immunofluorescent staining in the cytoplasm, whereas mature oocytes showed the immunofluorescent label concentrated in the nucleus. Metaphase chromosomes showed an intense immunofluorescence. The migration of cyclin B to the nucleus and its association with metaphase chromosomes in pig oocytes able to progress through meiosis resembled the subcellular localisation of cyclin B and the distribution of maturation promoting factor (MPF) in mitotic dividing cells.