Decondensation and Male Pronuclear Formation in Bovine Oocytes after Microinjection of Bovine Sperm Pretreated with Disulfide Bond Reducing Agents

Abstract

Effect of some reducing agents, their combination with other agents, and their concentration on changes in sperm nuclei and pronuclear formation was investigated. First, while treated with 50 mM DTT, 80% of the sperm had partly decondensed their nuclei after 0.5 h of treatment, and complete decondensation was observed in all the sperm after 10 min incubation in 5 mM DTT and 1% SDS. None of the sperm was seen dispersed 2 h after treatment with 50 mM GSH and 5% SDS. Second, the decondensation rate was dependent on the NaCl concentration when DTT was used as a reducing agent. Finally microinjection of sperm pretreated with 5 mM DTT resulted in a significantly higher male pronuclear formation rate 6 h postinjection (49%) than that (5.3%) of the heparin pretreated control. These results suggest that pretreatment of bovine sperm with DTT may affect the fertilization rate after microinjection.