Ultrastructural localization of enkephalin-like immunoreactivity in the rat adrenal medulla.

The PAP method was applied to adrenomedullary cells to demonstate the subcellular localization of ELI. The labeled cell-groups were identified from flat-embedded virbratome sections by light microscopy. Electron microscopy showed that the precipitate was associated with the storage granules of the cells. The number of labeled granules varied greatly from cell to cell. In corresponding to those showing heavy staining by light microscopy, all the granules were stained with precipitate. It is suggested that the peptide responsible for the ELI might be released together with the catecholamines.