α-neoendorphin-like immunoreactivity in medullary carcinoma of the thyroid

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Abstract
α‐Neoendorphin‐like immunoreactivities (α‐NE‐IR) were demonstrated in tissues from three patients with medullary carcinoma of the thyroid (MCT). A large amount of α‐NE‐IR was detected in the extracts of primary tumors and metastatic lymphatic tissues by a highly sensitive and specific radioimmunoassay (RIA). Gel filtration analyses showed two different molecular‐weight forms of the α‐NE‐IR: One eluted at the void fraction and the other at the position of [125I]‐α‐NE on Sephadex (Pharmacia Fine Chemical, Uppsala, Sweden) G‐50 chromatography. Immunohistochemical examination revealed the presence of α‐NE‐IR in the C‐cell carcinoma. These data presumably reflect that α‐NE, the opioid peptide derived from preproenkephalin B, is synthesized in the MCT. Cancer 59:277–280, 1987.