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  • Title: Sperm-immobilizing antibodies suppress an increase in the plasma membrane fluidity of human spermatozoa.
    Author: Nakagawa K, Yamano S, Kamada M, Maegawa M, Tokumura A, Irahara M, Saito H.
    Journal: Fertil Steril; 2004 Oct; 82 Suppl 3():1054-8. PubMed ID: 15474073.
    Abstract:
    OBJECTIVE: To clarify the mechanism by which capacitation is blocked by sperm-immobilizing antibodies, changes in the plasma membrane fluidity of human spermatozoa exposed to sperm-immobilizing antibodies were evaluated. DESIGN: In vitro cell culture study using human spermatozoa. SETTING: Department of Obstetrics and Gynecology, School of Medicine, The University of Tokushima. PATIENT(S): Semen samples were obtained from four healthy, fertile volunteers. INTERVENTION(S): The internalization of [3H]lyso-platelet activating factor (lyso-PAF) across the plasma membranes of human spermatozoa, which were exposed to sperm-immobilizing antibodies (antisperm group) or not exposed (control group), was measured at 20 and 60 minutes after the addition of a phospholipid probe using the modified albumin-back extraction method. MAIN OUTCOME MEASURE(S): The percentage of internalization of [3H]lyso-PAF across the plasma membrane of human spermatozoa. RESULT(S): Although the percentages of internalization of [3H]lyso-PAF (mean +/- SE) in the antisperm and control groups 20 minutes after addition of [3H]lyso-PAF were not significantly different (6.6% +/- 1.5% and 9.2% +/- 2.1%, respectively), at 60 minutes after the addition, the percentage in the antisperm group (9.0% +/- 1.3%) was significantly lower than that in the control group (13.4% +/- 1.3%). This inhibitory effect was diminished when spermatozoa exposed to sperm-immobilizing antibodies were incubated in an antibody-free medium. CONCLUSION(S): Sperm-immobilizing antibodies suppress the increase in internalization of an alkyl ester lysophospholipid probe in plasma membranes of human spermatozoa, and this inhibitory effect is reversible. Therefore, sperm-immobilizing antibodies suppress the fluidity of the plasma membranes of human spermatozoa, thus blocking capacitation.
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