ABSTRACT
<p><b>OBJECTIVE</b>To screen the stage-specific expression proteins during rats spermatogenesis, and to investigate the beta-actin expression and localization in the tissues of rat testicular.</p><p><b>METHODS</b>Highly enriched type A spermatogonia, pachytene spermatocytes and round spermatids were isolated by STAPUT method (sedimentation velocity at unit gravity, with 2% - 4% BSA gradient in DMEM/F12 medium) respectively to get the total proteins. The difference of protein expression between the three kinds of cells was analyzed by two-dimensional electrophoresis. Then the distribution of beta-actin in rat testicular tissues was investigated using specific anti-beta-actin antibodies by immunohistochemical method.</p><p><b>RESULTS</b>beta-actin was identified as a stage-specific expression protein by two-dimensional electrophoresis. beta-actin protein was more strongly expressed in type A spermatogonia and pachytene spermatocytes, but not in round spermatids. The immunohistochemical results showed that beta-actin was mainly located in the cytoplasm of type A spermatogonia and pachytene spermatocytes and in the nuclei of nearly mature spermatids.</p><p><b>CONCLUSION</b>beta-actin protein is a stage-specific expressed protein and may play an important role in spermatogenesis.</p>