CENTRIFUGATION ON PERCOLL GRADIENT ENHANCES FLUORESCENT LECTIN-BINDING ON HUMAN SPERM - A FLOW CYTOMETRIC ANALYSIS

Centrifugation on a Percoll gradient is commonly used to enrich sperm preparations in mobile forms prior to in vitro fertilization attempts. It has been suggested that this method also induces the capacitation of sperm, a step preceding the acrosomal reaction allowing egg fertili zation. The modifications of the acrosomal membrane involved in these physiological events likely include alterations of glycosylation patte rns. This hypothesis was investigated by comparing the membrane bindin g of 15 fluorescein-conjugated lectins on 60 samples of sperm, before and after Percoll centrifugation. The numbers of labeled sperm and the ir mean fluorescence intensity, recorded in flow cytometry, significan tly increased for 10 and 14 of the 15 lectins tested. Microscopic exam ination of the labeled sperm showed that the acrosome and equatorial p lates were more often labeled after Percoll centrifugation, confirming the hypothesis that this method modifies the glycosylation pattern of structures important for egg fertilization.