Comparison between propidium iodide and 7-amino-actinomycin-D for viability assessment during flow cytometric analyses of the human sperm acrosome.

Evaluation of the acrosome reaction can shed light on the fertilising competence of spermatozoa. To eliminate false-positive results when evaluating the acrosome status of human sperm cells, two viability probes propidium iodide (PI) and 7-amino-actinomycin D (7-AAD) were compared for their ability to stain nonviable cells post-fixation and permeabilisation. Both the mean fluorescence and % dead cells differed significantly with time (P < 0.0001). Unlike PI, 7-AAD did not leach from cells and fluorescence remained stable for up to 4 h. Furthermore, 7-AAD proved to be a proficient marker to exclude dead sperm cells during flow cytometric evaluation of ionophore-induced acrosome reaction.