Ultrastructural and immunocytochemical study of P1, protamine localization in human testis

Summary. Two monoclonal antibodies (MAbs) directed against human protamine P ₁ were realized. Anti- P ₁ specificity was assessed by western-blot and confirmed by elisa. Monoclonal antibody 97-3 was selected. Protamine P ₁, was specifically demonstrated in human testis by immunoelectron microscopy, using 97-3 MAb and an indirect post-embedding immunogold technique. Our results clearly demonstrated the precise time of appearance of P ₁ protamine in the nuclei of human spermatids. P ₁, first appeared in the nucleus of step 5 spermatids and its concentration was increased in steps 6–8 spermatids, cytoplasm was not labelled.