Detection of microfilaments in rat Sertoli cell ectoplasmic specializations with NBD-phallicidin

The identification of microfilaments contained within Sertoli cell ectoplasmic specializations (ES) in intact rat testes is reported. In order to determine the presence and configuration of ES during the cycle of the seminiferous epithelium, frozen sections of testes were prepared and stained with NBD-phallicidin (NBDP). Results revealed that Sertoli cell ES become most prominent immediately adjacent to acrosomal caps of spermatids, once these begin their elongation phase of maturation. Significant association of ES with spermatogenic cells earlier than round spermatids was not detected with NBDP. Intense staining of the ES continued up to the final stages preceding sperm release, and was followed by dissipation of the fluorescence. These results indicate that the disappearance of ES, as detected with NBDP, does not correlate precisely with sperm release.