[Frontiers in Bioscience 1, d146-160, August 1, 1996]
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INTERACTION OF HUMAN SPERMATOZOA WITH THE ZONA PELLUCIDA OF OOCYTE: DEVELOPMENT OF THE ACROSOME REACTION

Patricio Morales1 and Miguel Llanos2

1 P. Catholic University of Chile, Faculty of Biological Sciences. P. O. Box 114-D. Santiago, Chile.

2INTA, University of Chile, P. O. Box 138-11. Santiago, Chile.

2. INTRODUCTION

There is still debate about the composition of the human zona pellucida (ZP). SDS-PAGE of zona pellucida proteins under non-reducing conditions shows two to three main bands. The biological function of the individual components of ZP is just beginning to be recognized. Recombinant human ZP3 promotes the acrosome reaction and stimulates a protein with tyrosine kinase activity. Whether human zona pellucida or recombinant ZP3 can also stimulate sperm calcium influx is not known. Regarding the status of the sperm binding proteins for zona ligands, several candidates have been proposed. Among them are a galactosyltransferase, a D-mannosidase, a protein tyrosine kinase, and an unusual galactosyl receptor lectin. Clearly, the binding of the spermatozoa to the ZP triggers the acrosomal exocytosis. The mechanism (s) by which the acrosome reaction (AR) is stimulated by the ZP seems to be related to the production and sequential action of several intracellular messengers, with a crucial function in the development of the AR. It has been suggested that progesterone and the zona pellucida may synergistically act to promote acrosomal exocytosis in mouse. Whether the same is true in humans is not yet known; however, progesterone-treated human spermatozoa bind to the ZP in higher numbers than the non-treated spermatozoa. Other molecules have been recognized that serve a modulatory role in the spermatozoa-ZP binding process. The aim of the present review is to summarize the current knowledge about human spermatozoa-ZP interactions and the mechanisms accounting for the AR.

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