Histochemical demonstration of zinc ions in human epididymis using autometallography

A recently described autometallographic technique, allowing demonstration of chelatable zinc in human biopsy material, was applied to cryostat sections from biopsies of human epididymis. Sections from the rat epididymis were used as control materials to examine the quality of the method compared with a previously used autometallographic method. The human epididymis exhibits heavy staining in the head of the epididymis and only small amounts of zinc in the body and tail of the organ. The zinc staining was found in the apical part of the ciliated cells and in the lumen. The present technique can be used to localize zinc ions at ultrastructural levels. Zinc grains were localized in lysosome-like bodies and secretory granules of the ciliated cells. The luminal staining was present as free, evenly dispersed zinc grains or attached to sperm cells and stereocilia in the lumen. The large differences in staining patterns along the epididymal tract in humans and rats suggest that zinc ions are important for the maturation of sperm cells.