monoiodotyrosine and Pheochromocytoma

Pancreatic polypeptide (PP) and neuropeptide Y (NPY) belong to a family of regulatory peptides which hold a distinct tertiary structure, the PP-fold, even in dilute aqueous solution. High-affinity receptors, specific for both PP and NPY, are described on the rat phaeochromocytoma cell line, PC-12. The binding of [125I-Tyr36]PP to PC-12 cells was inhibited by concentrations of unlabeled PP which correspond to physiological concentrations of the hormone, 10(-11)-10(-9) mol/l. The affinity of the receptor for the neuropeptide, NPY, was 10(2)-times lower than that of the PP receptor. C-terminal fragments of both PP (PP24-36) and NPY (NPY13-36) were between 10(2)- and 10(3)-times less potent in displacing the radiolabeled 36-amino-acid peptides from their respective receptors. It is concluded that PC-12 cells are suited for structure-function studies of the PP-fold peptides and studies on the cellular events following cellular binding of PP-fold peptides.

Topics: Adrenal Gland Neoplasms; Animals; Binding, Competitive; Iodine Radioisotopes; Kinetics; Monoiodotyrosine; Neuropeptide Y; Pancreatic Polypeptide; Peptide Fragments; Pheochromocytoma; Rats; Receptors, Gastrointestinal Hormone; Receptors, Neuropeptide Y; Receptors, Neurotransmitter; Tumor Cells, Cultured

Of the metabolic precursors of the catecholamines fixed by the adrenal medulla, 131I marked thyrosine was chosen as a radio-tracer. 6 positive results out of 11 pheochromocytomas confirmed at surgery were obtained in a series of 23 patients. This result is comparable with the results of arteriography but there are more false positives, reflecting the insecurity of this technique which is otherwise quite innocuous.

Topics: Adrenal Gland Neoplasms; Adrenal Medulla; Adult; Aged; Angiography; Female; Humans; Hypertension; Infant; Iodine Radioisotopes; Male; Methods; Middle Aged; Monoiodotyrosine; Pheochromocytoma; Radionuclide Imaging

Topics: Adrenal Gland Neoplasms; Humans; Iodine Radioisotopes; Monoiodotyrosine; Pheochromocytoma; Radionuclide Imaging