Adrenocorticotropin, β-Endorphin, and β-Mipotropin in Normal Thyroid and Lung: Possible Implications for Ectopic Hormone Secretion

The expression of the proopiomelanocortin (POMC) gene by normal lung and thyroid was examined by measurement of the content of ACTH, βMipotropin (βLPH), and β-endorphin (βEP) in porcine lung and thyroid tissue. Acid extracts of normal porcine lung and thyroid tissue each contained appreciable amounts of immunoreactive (ir) ACTH, ir-βLPH, and ir-βEP. The content of ir-βLPH in both tissues exceeded by severalfold, on a molar basis, the content of ir-ACTH and ir- βEP, suggesting that the common precursor POMC was processed predominantly to peptides other than ir-ACTH and ir- βEP. A porcine thyroid extract (Calcitare, porcine calcitonin, Armour) showed equivalent levels of βEP-like immunoreactivity and bioactivity, measured by opiate radioreceptor assay; in contrast, ACTH-like bioactivity, measured by rat zona fasciculata steroidogenesis, was only 4% of ACTH-like immunoreactivity. On reversed phase high performance liquid chromatography, Calcitare showed multiple peaks of ACTH-like immunoreactivity, one of wh...