Presence of dynorphin-like immunoreactivity in pheochromocytomas.

Using a highly specific and sensitive radioimmunoassay for dynorphin(1-13), dynorphin-like immunoreactivity (dynorphin-LI) was detected in two extramedullary pheochromocytomas and a medullary pheochromocytoma. The contents of dynorphin-LI of two extramedullary and a medullary tumors were 9.2, 2.2, and 34.0 pmole/g, respectively. Gel chromatographic studies of tumor extracts on Sephadex G-50 revealed a peak of dynorphin-LI eluting at the same position as dynorphin-LI contaminated in porcine ACTH extract (Sigma) and another portion of dynorphin-LI eluting in a range of molecular weights larger than that of dynorphin-LI in porcine ACTH extract. These results indicate the presence of dynorphin and possibly its precursor peptide(s) in pheochromocytoma.