FIGURE 7.

Patterns of phosphatidylserine-exposure in viable stallion sperm. Spermatozoa were incubated either in the presence of 30 mM bicarbonate (Tyr_Bic) or Tyr_Bic containing 1 mM caffeine (Tyr_Bic+caffeine). An exposure of phosphatidylserine (PS) in viable (Hoechst 33258 negative) sperm was detected using Annexin V-Fluos (n = 3 stallions). PNA-Alexa Fluor647 was included as an additional marker for acrosome integrity. Staining patterns for Annexin V were observed in the acrosomal area [(A), arrow], across the complete head region [(B), arrow] or in the complete head and the midpiece [(C), arrows]. The frequency of each pattern in the viable sperm population was determined after 30 and 60 min incubation time (D). Differing letters (A–C) indicate significant differences between the abundance of each labelling pattern for Annexin V. There were no significant differences between timepoints (n = 12 samples per pattern; p < 0.05).