- Studies on adrenorphin in pheochromocytoma.
Studies on adrenorphin in pheochromocytoma.
We studied the secretion and tissue contents of adrenorphin in human pheochromocytomas. In 17 human pheochromocytomas from 11 patients, we found a remarkably wide distribution in immunoreactive adrenorphin levels (3-7771 pg/mg tissue). Adrenomedullary pheochromocytomas contained a significantly larger amount of immunoreactive adrenorphin (2295 +/- 1092 pg/mg, mean +/- SE) than did extramedullary ones (17.8 +/- 8.4 pg/mg). Gel chromatographic studies revealed that immunoreactive adrenorphin consisted largely of material emerging at the position of synthetic adrenorphin in both pheochromocytoma and normal adrenal medulla tissue. Nicotine (10(-5) M) significantly stimulated the secretion of immunoreactive adrenorphin as well as catecholamines from cultured human pheochromocytoma cells. Adrenorphin was a more potent inhibitor of catecholamine secretion evoked by 10(-5) M nicotine than was met-enkephalin in cultured human pheochromocytoma cells. The 50% inhibitory concentrations (IC50) were 1.1 X 10(-6) and 6.5 X 10(-5) M for adrenorphin and met-enkephalin, respectively. The effect of adrenorphin was much the same as that of dynorphin-(1-13) (IC50, 1.0 X 10(-6) M) and BAM-12P (IC50, 4.5 X 10(-6) M). These results indicate the presence and secretion of adrenorphin in human pheochromocytomas. Adrenorphin may play an important role in regulating catecholamine secretion in human pheochromocytoma.