RESUMO
Eukaryotic cells have internal scaffolding of microtubules cytoskeleton that gives them their characteristic shapes. We analyzed by immuno-fluorescence the shift and distribution of tubuline during in vitro bull sperm nuclei swelling by the action of heparin-reduced glutathione physiological decondensing agents. Sperm tubulin display a pattern that shows tubulin fluorescence all over the head, leaving the acrosome tip devoid of tubulin. In the second stage we can observe that the acrosomal zone is practically devoid of fluorescence and a net of fluorescent microtubules that seems to be anchored in the basal plate in the postacrosomal region. It is also possible to observe green spots of tubulin fluorescence in the nucleus periphery, that might represent clusters of chromatin hub-like bodies and/or the microtubule organizing center (MTOC). In the third stage, practically all tubulin moves backwards to the basal plate in the neck region of the sperm nuclei remaining in only the green fluorescence spots in the periphery of the swollen sperm nuclei. The results allow us to assume that tubulin mechanism rearrangement is considered to be necessary for the normal fertilization process.