EFFECT OF SPERM VIABILITY, PLASMALEMMA INTEGRITY, AND CAPACITATION ONPATTERNS OF EXPRESSION OF MANNOSE-BINDING SITES ON HUMAN SPERM

The objective of this study was to characterize patterns of surface ex pression of mannose-binding sites (MBS) on human spermatozoa while eva luating the influence of sperm viability, plasma membrane integrity, a nd capacitation. D-Mannose binding sites were visualized by fluorescen ce microscopy using fluoresceinated mannose-enriched bovine serum albu min (FITC-DMA). To verify the probe specificity, 200 mM D-mannose and D-mannosylated albumin 200 mu g/mL (DMA) were used as competitive inhi bitors. Fluoresceinated bovine serum albumin (FITC-BSA) was used as co ntrol. Sperm membrane integrity was checked with a hypoosmotic swellin g test (HOST) and sperm viability with Hoechst 33258 at 1 mu g/mL. Via ble spermatozoa with intact plasma membrane presented two main pattern s: light bar (weak labeling of the equatorial segment) and slot (label ing of the pre- and postequatorial areas with a negative band in betwe en). These patterns were significantly inhibited when unlabeled D-mann ose or DMA were included in the medium. The percentages of spermatozoa displaying these two patterns increased significantly during capacita tion. Nonviable spermatozoa with altered plasma membrane integrity pre sented multiple fluorescent patterns, all of which were present when F ITC-BSA was used as the marker. None of them could be suppressed by un labeled D-mannose or DMA. Viable spermatozoa displayed two main patter ns which increased their incidence with capacitation and may be the on ly specific patterns for surface MBS. Other patterns detected in sperm atozoa bearing altered plasma membranes may be due to nonspecific BSA binding or intracellular MBS recognition.