Capacitation and acrosome reactions in human spermatozoa monitored by a chlortetracycline fluorescence assay

Human spermatozoa were incubated in culture medium containing human serum albumin (HSA) to promote capacitation, which was monitored by a rapid chlortetracycline (CTC) fluorescence assay. Four CTC fluorescence patterns were readily distinguished, one of which appeared to be correlated with capacitated sperm. When capacitated sperm were treated with either ionophore A23187 or acid-solubilized mouse zonae pellucidae to induce the acrosome reaction, the CTC assay identified acrosome-reacted sperm by lack of fluorescence on the head. Fresh sperm would not undergo the induced acrosome reaction. The percentages of acrosome-reacted sperm identified by the CTC assay in induced and control populations were the same as those identified by the presently used indirect immunofluorescence and triple stain assays.