Figure 6
Predominant patterns of fluorescent filipin-cholesterol labelling and the frequency of each of these patterns observed on fixed boar spermatozoa following incubation in capacitating and non-capacitating conditions for 2 h. (A) Uniform filipin labelling was observed across the entire sperm head in non-capacitating cells (1). In capacitating cells, filipin-cholesterol complexes concentrate in the apical and pre-equatorial region of the sperm head (indicated by bracket; 2). As in (2) but there were filipin-cholesterol complexes residing in the post-equatorial region of the sperm head (post-equatorial region indicated by an arrow; 3). Cells that exhibited a loss of filipin-cholesterol complexes were identified by the lower fluorescence when compared to non-responsive cells or those with cholesterol redistribution (indicated by arrows; 4). Scale bar = 10 µm. (B) Spermatozoa exposed to TALP supplemented with or without cAMP up-regulators (white bar and white hatched bar, respectively) or TALP without bicarbonate but supplemented with cAMP up-regulators (dark gray hatched bar) demonstrated a significant decrease in the percentage of non-responsive cells and increase in patterns indicative of cholesterol redistribution and efflux. Results are based on six independent samples and presented as the mean ± SEM. **P < 0.01 and ***P < 0.0001 indicate differences from the non-capacitating control.
