Cytochemical demonstration that acrosin is unavailable in intact ejaculated boar and bull spermatozoa

The cytochemical localization of acrosin (EC 3.4.21.10) was investigated using a fluorescent technique, based on the use of fluorogenic substrates, derivatives of 4-methoxy-beta-naphthylamine, which liberate a fluorescent tag that, if coupled to 5-nitrosalicylaldehyde, generates an insoluble, fluorescent product. From the data obtained from boar and bull spermatozoa that had been subjected to different treatments, we have found that the acrosomal, trypsinlike proteinase is practically inaccessible in intact, freshly ejaculated spermatozoa. Acrosin activity was detected after subjecting the spermatozoa to a treatment that simulates the process they undergo at the moment of fertilization, showing a particulate localization in the acrosome of some of the spermatozoa.