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.

Human sperm motility, capacitation and acrosome reaction are impaired by 2-arachidonoylglycerol endocannabinoid.

The endocannabinoids are cannabinoids synthesized by mammalian tissues. These compounds are closely related to the regulation of the male reproductive system. However, little is known about the effects produced by 2-arachidonoylglycerol (2AG) on in vitro human sperm functions. This study was undertaken to determine the effects produced by 2AG on fresh human sperm and in the capacitation technique. Semen samples from healthy young men were exposed to different concentrations of 2AG before and during capacitation technique. In this work, we have demonstrated that 2AG induces the spontaneous acrosome reaction and reduces progressive motility in fresh human sperm. During the capacitation technique, sperm becomes more sensitive to low concentrations of 2AG, triggering the acrosome reaction and inhibiting protein phosphorylation. In summary, 2AG affects the in vitro functionality of human sperm by reducing motility, inhibiting capacitation and triggering the acrosome reaction.