Destruction of protamine in human sperm inhibits sperm binding and penetration in the zona-free hamster penetration test but increases sperm head decondensation and male pronuclear formation in the hamster-ICSI assay.
OBJECTIVE
Our purpose was to investigate the fertilizing ability of human protamine-damaged sperm in a heterologous system using hamster oocytes.


METHODS
The protamine of the sperm were damaged by exposure to dithiothreitol, a disulfide-reducing agent. Their ability to penetrate and form male pronuclei were investigated using the zona-free hamster penetration test and the hamster-intracytoplasmic sperm injection assay, respectively.


RESULTS
The zona-free hamster penetration test revealed that protamine-damaged sperm are unable to bind and penetrate the hamster oocyte. On the other hand, hamster-intracytoplasmic sperm injection assay results showed that 56.9% and 39.2% of the injected oocytes developed male pronuclei in protamine-damaged and live-intact sperm groups, respectively, with a significant difference in these rates (P < 0.01).


CONCLUSIONS
This study shows that protamine-damaged sperm are able to undergo sperm head decondensation and male pronuclear formation only when injected into the ooplasm, although they cannot bind and penetrate through the zona and enter the ooplasm.
Ahmadi
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Department of Obstetrics and Gynecology, National University of Singapore, Singapore.
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D000165:Acridine Orange / Q000737:chemistry; D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D006224:Cricetinae; D004229:Dithiothreitol / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro; D005456:Fluorescent Dyes / Q000494:pharmacology; D006494:Heparin Antagonists / Q000378:metabolism*; D006801:Humans; D007248:Infertility, Male / Q000503:physiopathology*; D008297:Male; D008647:Mesocricetus; D051379:Mice; D008845:Microinjections; D009865:Oocytes / Q000502:physiology; D011479:Protamines / Q000378:metabolism*; D013077:Sperm Head / Q000502:physiology; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology*; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D006063:Chorionic Gonadotropin; D005456:Fluorescent Dyes; D006494:Heparin Antagonists; D011479:Protamines; D013439:Sulfhydryl Reagents; D000165:Acridine Orange; D004229:Dithiothreitol