Presence of Galanin-Like Immunoreactivity in Nontumorous Corticotrophs and Corticotroph Adenomas of the Human Pituitary

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Abstract
Galanin is a 29-amino acid neuropeptide widely distributed in the central nervous system. Galanin-like immunoreactivity (galanin-LI) was investigated in 23 nontumorous human adenohypophyses and 27 pituitary adenomas. Galanin-LI was demonstrated by immunohistochemistry on formalin-fixed paraffin-embedded sections, using the avidin-biotin peroxidase complex method. All 23 nontumorous pituitaries showed the presence of galanin-positive cells which were similar to the corticotrophs in shape, size, histological features, and distribution. Immunoreactivity based on the study of mirror sections was found to be present in the cytoplasm of corticotrophs, indicating that galanin-LI colocalizes with ACTH. Crooke''s cells and basophilic cells spreading to the posterior lobe (basophil invasion) were also positive for galanin. No galanin-LI was seen in lactotrophs of the human pituitaries, including 4 estrogen-treated men and 4 pregnant women. Varying numbers of tumor cells in 13 of 18 corticotroph adenomas were positive for galanin. Galanin-LI and ACTH were coexpressed in the cytoplasm of the same adenoma cells. In 19 pituitary adenomas composed of cells other than corticotrophs, no galanin-LI was noted. This study is the first report providing evidence of the presence of galanin-LI in corticotrophs of the human pituitary.