Progesterone Triggers a Wave of Increased Free Calcium during the Human Sperm Acrosome Reaction

• Published in: Developmental biology Vol. 182; no. 1; pp. 67 - 75
• Main Authors: Meizel, Stanley, Turner, Kenneth O., Nuccitelli, Richard
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.02.1997
• Subjects: Acrosome - drug effects; Acrosome - physiology; Calcium - metabolism; Female; Fluorescent Dyes; Fura-2; Humans; Male; Microscopy, Video; Picrotoxin - pharmacology; Progesterone - pharmacology; Receptors, GABA-A - physiology; Sperm Capacitation; Sperm-Ovum Interactions; Time Factors
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1006/dbio.1997.8477

The mammalian sperm acrosome reaction (AR), an essential fertilization event, requires an influx of Ca 2+. The Ca 2+increase occurring in the human sperm head during the AR initiated by progesterone, a putative in vivoAR initiator, was investigated using video-image analysis with fura-2, a fluorescent Ca 2+probe. Progesterone treatment of capacitated human sperm resulted in a wave-like increase in sperm head cytosolic [Ca 2+] ithat appears to increase fastest in a region near the equatorial segment and then spreads throughout the rest of the head. The progesterone-mediated Ca 2+increase in the sperm head was strongly inhibited and the wave eliminated by picrotoxin, a blocker of GABA Areceptor/Cl −channels and an inhibitor of the progesterone-mediated Cl −efflux and progesterone-initiated AR of human sperm. These results are the first to detect a ligand-mediated Ca 2+wave in sperm and to suggest that Cl −efflux influences Ca 2+influx during the AR.