Immunocytological detection and localization of a peptide reacting with an alpha-endorphin antiserum in the corticotropic and melanotropic cells of the trout pituitary (Salmo irideus Gibb).

In the pituitary of the trout, the corticotropic and melanotropic cells display a strong immunocytological reaction with alpha-endorphin antiserum. This reaction persists even when alpha-endorphin antisera treated with beta-1-24ACTH or alpha-MSH are used. In the absence of pharmacological tests on the endorphic potencies of the compounds involved in the immunoreaction, it is not yeat clear whether this reaction is due to the presence of an alpha-endorphin-like peptide or simply an immunologically related peptide without the properties of endorphin. However, the presence of such peptides in the fish pituitary is interesting from the comparative point of view.