Detection of human sperm acrosome reaction: comparison between methods using double staining, Pisum sativum agglutinin, concanavalin A and transmission electron microscopy.

The acrosome reaction is an important marker for human sperm function. Since different laboratory techniques may be used for the detection of this exocytotic process, the purpose of the present study was to compare three common markers [Pisum sativum agglutinin (PSA), concanavalin A (ConA), double staining] and transmission electron microscopy for identification of acrosomal changes. Preliminary findings had demonstrated that similar results were achieved with Trypan Blue and Hoechst 33258 staining. Therefore, supravital stainings were omitted. In various experiments, human spermatozoa were treated with two concentrations (10 and 3.3 microM) of calcium ionophore A23187 for 15, 30 and 60 min after capacitation for 3 and 6 h at 37 degrees C. The percentages of spermatozoa with acrosomal loss detected by fluorescein isothiocyanate (FITC)-ConA were consistently lower than those obtained by double staining or FITC-PSA, which showed comparable results. Following 6 h of capacitation and incubation with 10 microM ionophore for 1 h at 37 degrees C, 25.9 +/- 15.7% of all spermatozoa showed almost complete loss of the acrosomal content. Binding of FITC-ConA to the acrosomal region was observed in 27.0 +/- 13.2% of spermatozoa obtained from the same sample. FITC-ConA and double staining or FITC-PSA detect different stages of the acrosome reaction and may be helpful for a differentiated evaluation of this sperm function.