LECTIN-BINDING SITES ON HUMAN SPERM DURING ACROSOME REACTION - MODIFICATIONS JUDGED BY ELECTRON-MICROSCOPY FLOW-CYTOMETRY

Biochemical surface modifications occur during the capacitation and ac rosome reaction of human sperm and among those, variations in the expr ession of carbohydrates moieties. A sequential study was performed wit h electronic microscopy and flow cytometry techniques, where the bindi ng of 4 lectins was assessed on normal human sperm samples during in v itro induction of the acrosome reaction with calcium ionophore A-23187 . Triticum, vulgaris agglutinin (WGA) was shown to bind strongly the w hole surface of sperm before induction of the acrosome reaction, and i n lesser amounts after incubation with calcium ionophore. Arachis hypo gea agglutinin (PNA) and mostly Concanavalia ensiformis agglutinin (Co n-A) and Ulex europaeus agglutinin (UEA-I) binding evolved in an oppos ite pattern with an increase of the labeling parallel to that of GB24 antibody binding. Electron microscopy showed that the fluorescence pat terns observed correlated with increased access to the inner membrane of the acrosome. This was significant 60 min after the induction of ac rosome reaction. Lectin binding could be a useful tool to examine the ability of sperm samples to undergo the acrosome reaction.