Capacitation and acrosome reaction changes α-tubulin immunodistribution in human spermatozoa

Tubulin is a protein constituent of cytoskeletal microtubules, closely related to sperm motility. However, the changes in tubulin distribution following capacitation and acrosome reaction are poorly understood. This study immunolocalized and quantified the expression of α-tubulin in fresh, capacitated and acrosome-reacted samples. Immunocytochemical data showed that in capacitated and acrosome-reacted spermatozoa, α-tubulin is labelled throughout most of the flagellum (⩾66.66%). However, the mean α-tubulin-labelled area in these samples was significantly lower than in fresh samples (P < 0.05). Thus, there are different sperm clusters distinguished by their α-tubulin immunoreactivity and this could be directly linked to structural changes following capacitation and acrosome reaction.