Acrosome-reacted guinea pig spermatozoa become fusion competent in the presence of extracellular potassium ions.
Guinea pig spermatozoa are able to undergo capacitation and the acrosome reaction in a K+-free (-deficient) medium. However, they are unable to fuse with eggs unless they are exposed to a millimolar concentration of extracellular K+ during or after the acrosome reaction. Apparently, the plasma membrane over the equatorial segment gains the ability to fuse with eggs in the presence of K+ during and/or after the acrosome reaction. Once it becomes fusible, the membrane retains its fusibility even in a K+-deficient medium. Rb+ is almost as effective as K+ in rendering the sperm membrane fusible. Li+ and Cs+ are less effective. The molecular mechanism by which K+ renders acrosome-reacted spermatozoa fusion competent is unknown, but it may involve K+-mediated efflux of H+ from the spermatozoa.
Yanagimachi
R
R
Department of Anatomy and Reproductive Biology, University of Hawaii, School of Medicine, Honolulu 96822.
Bhattacharyya
A
A
D000177:Acrosome / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000502:physiology; D006224:Cricetinae; D003470:Culture Media; D005260:Female; D005306:Fertilization; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D011188:Potassium / Q000502:physiology*; D011247:Pregnancy; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology*
D003470:Culture Media; D011188:Potassium; D002118:Calcium