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Hum Reprod. 2005 Dec;20(12):3459-68. Epub 2005 Aug 19.

Phosphatidylserine externalization in human sperm induced by calcium ionophore A23187: relationship with apoptosis, membrane scrambling and the acrosome reaction.

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1
Laboratoire de Biologie de la Reproduction, GIMAP, Hôpital Nord, 42055 Saint-Etienne, France.

Abstract

BACKGROUND:

Translocation of phosphatidylserine (PS) from the inner to the outer leaflet of the plasma membrane is a modification of the lipid architecture occurring in sperm. This is one of the earliest signs of apoptosis that can be monitored by the calcium-dependent binding of annexin V.

METHODS AND RESULTS:

Flow cytometric analysis of annexin V binding was performed. Calcium ionophore A23187 led to a significant increase in the proportion of living sperm with PS exposure: 7.3 3.2% of cells in the untreated ejaculate versus 47.5 5.6% of cells after 1 h of incubation with A23187. Conversely, diminution of mitochondrial membrane potential [DiOC6(3)/propidium iodide (PI) assay], caspase activation [fluorescein isothiocyanate (FITC)-Val-Ala-Asp-fluoromethylketone (VAD-FMK)/PI assay], increased plasma membrane permeability (Yo-Pro-1/PI assay) and increased DNA fragmentation [TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end labelling assay], which are among the main signs of apoptosis, were not observed in sperm, even after 4 h of incubation with A23187. However, A23187 significantly increased the proportion of sperm with plasma membrane scrambling and with a reacted acrosome, as detected with the merocyanine 540 probe (M540) and the monoclonal anti-human CD46-PE antibody respectively.

CONCLUSIONS:

Our results suggest that PS exposure in human sperm, as induced by A23187, is mainly related to the acrosome reaction rather than to apoptosis.

PMID:
16113043
DOI:
10.1093/humrep/dei245
[Indexed for MEDLINE]
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