Ca2+-related changes in the capacitation state of human spermatozoa assessed by a chlortetracycline fluorescence assay

Chlortetracycline (CTC) fluorescence patterns were used to assess Ca 2+ -related changes in the capacitation state of human spermatozoa incubated under conditions that would affect their intracellular Ca 2+ levels. Initial experiments were designed to identify consistently occurring patterns and to correlate these with acrosomal status. Incubation for up to 1 h with the ionophore A23187 (10 μmol l -1 ), known to promote capacitation and acrosomal exocytosis, allowed the identification of three different CTC staining patterns which were very similar to those described for mouse spermatozoa