Immunocytochemical localization of protamine in the spermatids of the ram

Pure ram protamine isolated from epididymal spermatozoa was used to raise antisera in castrated rabbits. The antibodies were visualized in the electron microscope using the method of Moriarty and Halmi 1972] with either peroxidase or coupling with colloidal gold. The gold gave better contrast but lower afinity than the peroxidase method. With the use of fixation according to Thiery and Rambourg 1976] and thick sections treated with hydrogen peroxide, it was possible to detect the protamine in the cytoplasm near the flagellum and the chromatoid body of step 12 spermatids. It was concluded that protamine enters the nucleus and concentrates at that step in the ram.