Packaging of Mammalian Paternal Genome and Male Pronuclear Formation

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DNA-stability and thiol-disulfide status of rat sperm nuclei was observed during maturation in the epididymis and during penetration to the oocytes in vivo. When spermatids and spermatozoa were stained with acridine orange (AO) after fixation with acetic alcohol, the ratio of red/green fluorescence under a confocal microscope decreased until caput epididymis. On the other hand, when spermatozoa were labeled with rnBBr the fluorescence intensities gradually decreased during transportation of spermatozoa from testis through epididymis. The ratio of red/green AO fluorescence increased during penetration of zona pellucida and sperm decondensation. When spermatozoa in the perivitelline space were labeled with mBBr and examined fluorescence was detected. These results demonstrate that DNA stability against acid appears to be ahead of the oxidization of protamine during sperm maturation in the epididymis and that an initial event of the unpackaging process in rat genome begins during or just … More after zona-penetration but before penetration into the ooplasm.The contents of glutathione and other thiols in rat eggs were examined during sperm penetration and pronuclear formation by high-performance liquid chromatography with fluorescence detection. Reduced glutathione (GSH) content was higher in unfertilized oocytes and penetrated eggs with a decondensed sperm nucleus than eggs at the pronuclear stage. The content of oxidized glutathione (GSSG) was not different among experimental groups. The ratio of GSSG/GSH was not different during fertilization. Although reduced cysteinylglycine content did not changed among experimental groups, oxidized form of cysteinylglycine increased between sperm decondensation and pronuclear formation. Low contents of cystine were detected during fertilization but cysteine and gamma-glutamylcysteine were not detected in any treatment groups. These results demonstrate that GSH content in rat eggs decreases between sperm decondensation and pronuclear formation, probably due to the increased activity of gamma-glutamyl transpeptidase. Less