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Progesterone-Mediated Efflux of Cytosolic Chloride During the Human Sperm Acrosome Reaction

https://doi.org/10.1006/bbrc.1995.2197Get rights and content

Abstract

Progesterone is capable of initiating the mammalian sperm acrosome reaction in vitro and is a putative initiator of this essential fertilization event in vivo. Our previous work has suggested that progesterone initiates the human sperm acrosome reaction, at least in part, by activating a unique steroid receptor/Cl channel resembling a γ-aminobutyric acidA receptor/Cl channel (γ-aminobutyric acidA-like receptor/Cl channel). Here, the fluorescent intracellular Clprobe, 6-methoxy-N-ethylquinolinium, was used to detect qualitative changes in sperm cytosolic Cl. We demonstrate that progesterone can mediate a rapid transient decrease of human sperm cytosolic Cl inhibitable by the γ-aminobutyric acidA receptor/Cl channel antagonists picrotoxin and (+)-bicuculline (which also inhibit the acrosome reaction). These results support the involvement of a γ-aminobutyric acidA-like receptor/Cl channel in the P-mediated human acrosome reaction and are the first to demonstrate that a rapid Cl efflux plays a role in that event.

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