Cellular biology of capacitation and the acrosome reaction

For successful fertilization in mammals, sper-matozoa must complete capacitation and then undergo the acrosome reaction, an exocytotic process that allows cells to bind to and then penetrate the zona pellucida. After penetration has been achieved, acrosome-reacted cells are capable of fusing with the oocyte plasma mem-brane, thereby activating the oocyte and setting in train the completion of the second meiotic division and the initiation of the metabolic events that will sustain early embryonic develop-ment. Current evidence indicates that mechan-isms controlling the intracellular Ca2+ concentration [Ca2+]j play pivotal roles in con-trolling sperm fertilizing ability; it is these mechanisms which will be discussed here. Key words: acrosome reaction/fertilization/ intracellular Ca2+ concentration/sperm capac-itatio