Sperm-immobilizing antibodies suppress an increase in the plasma membrane fluidity of human spermatozoa.
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.


METHODS
In vitro cell culture study using human spermatozoa.


METHODS
Department of Obstetrics and Gynecology, School of Medicine, The University of Tokushima.


METHODS
Semen samples were obtained from four healthy, fertile volunteers.


METHODS
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.


METHODS
The percentage of internalization of [3H]lyso-PAF across the plasma membrane of human spermatozoa.


RESULTS
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.


CONCLUSIONS
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.
Nakagawa
Koji
K
Department of Obstetrics and Gynecology, School of Medicine, The University of Tokushima, Japan. nakagawa-kj@ncchd.go.jp
Yamano
Shuji
S
Kamada
Masaharu
M
Maegawa
Masahiko
M
Tokumura
Akira
A
Irahara
Minoru
M
Saito
Hidekazu
H
D000906:Antibodies / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D006801:Humans; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects*; D010972:Platelet Activating Factor / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics; D013081:Sperm Motility / Q000187:drug effects*; D013094:Spermatozoa / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors
D000906:Antibodies; C029271:O-deacetyl platelet activating factor; D010972:Platelet Activating Factor