[Ultrastructural histochemical study of the mammary gland of the lactating rat].

The authors report the results of their ultrastructural study on the lactating mammary gland of the rat using Grimelius' silver stain, modified for electron microscopy. The granules of the gland proteic ésocrine secretion are positive to silver impregnation, both within the cytoplasm and in the alveolar lumen. These results are interesting since they suggest that Grimelius' stain positive structures, in the mammary gland, should not be necessarily interpreted as endocrine, at least in the rat.