Co-existence of enkephalin and adrenalin in the frog adrenal gland

By means of immunohistochemistry combined with formaldehyde-induced fluorescence microscopy, met-enkephalin-like immunoreactivity was found to occur in the adrenalin -cells of frog adrenal glands. Immunoelectron microscopy demonstrated that the immunoreactive material is confined to the secretory granules. These findings suggest the concomitant release of enkephalin and adrenalin by exocytosis.