Immunohistochemical Localization of y-Endorphin in the Rat Pituitary Gland and Hypothalamus*

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Abstract
To gain more information about cells and organelles involved in the secretion of y-endorphin in the rat pituitary gland, an immunohistochemical localization of this peptide was conducted at both light and electron microscopic levels. Using an antiserum to γ-endorphin which shows little cross-reactivity with βMipotropin (β-LPH) and β-endorphin, it has been demonstrated that γ-endorphin is present in all cells of the intermediate lobe and the corticotropic cells of the anterior lobe. At the electron microscopic level, Staining for γ-endorphin was restricted to the secretory granules which also contain ACTH and β-LPH, suggesting that all of these peptides are released concomitantly during exocytosis. In the hypothalamus, immunostaining possibly related to both γ- and β-endorphin but not to β-LPH was also observed in nerve fibers and not in cell bodies. (Endocrinology106: 1512, 1980)