Studies related to progesterone-induced hamster sperm acrosome reaction.
Experiments were designed to characterize the effect of progesterone on the hamster sperm acrosome reaction (AR). Progesterone stimulated exocytosis of previously capacitated spermatozoa in a dose-dependent manner. Progesterone-3-(O-carboxymethyl)oxime:BSA conjugate also induced AR when added to capacitated sperm suspensions. EGTA and La3+, added 10 min before progesterone, completely abolished the steroid-stimulatory effect. Benzamidine, a trypsin inhibitor, also inhibited AR when added to sperm cells 10 min before progesterone. This effect was avoided when spermatozoa were treated with the Ca2+ ionophore ionomycin. Conversely, the H+ ionophore FCCP, or the Na+/K+ ionophore nigericin, did not prevent the effect of the inhibitor. Results suggest that progesterone acts on the hamster sperm plasma membrane to stimulate exocytosis, which requires external Ca2+ and presumably Ca2+ influx. In addition, a sperm trypsin-like protease may be part of the mechanism by which progesterone stimulates AR. Since the ionomycin-induced AR does not require this proteolytic activity, the possible involvement of such an enzyme in the progesterone-stimulated Ca2+ influx necessary for the occurrence of AR is discussed.
Llanos
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MN
Unidad de Biología de la Reproducción, INTA, Universidad de Chile, Santiago, Chile.
Anabalón
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MC
D000177:Acrosome / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001550:Benzamidines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D008297:Male; D011374:Progesterone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D013075:Sperm Capacitation; D013997:Time Factors
D001550:Benzamidines; D015842:Serine Proteinase Inhibitors; D011374:Progesterone; C032157:benzamidine; D002118:Calcium