Immunoreactive endothelin in pheochromocytomas

The presence of endothelin (ET) in tumor tissue and plasma of patients with pheochromocytoma was studied by radioimmunoassay. Immunoreactive (ir-) ET concentrations in 12 pheochromocytomas ranged from 66 to 253 fmol per gram wet tissue (gwt) (146 ± 20 fmol/gwt, mean ± SEM). These values were not significantly higher than tissue ir-ET concentrations of two primary aldosteronism (66 and 132 fmol/gwt) and three normal adrenal glands (71-120 fmol/gwt) (0.05 < p < 0.1). However, tumor tissue ir-ET concentrations in six of the 12 pheochromocytomas were higher than 132 fmol/gwt (the upper value of the control tissues). Sephadex G-50 column chromatography and reverse-phase high-performance liquid chromatography of pheochromocytoma tumor extracts showed a major peak eluting at an identical position to synthetic ET-1. Plasma ir-ET concentrations of pheochromocytomas (1.4 ± 0.9 fmol/ml, n = 17) were not significantly different from those of patients with essential hypertension (1.0 ± 0.7 fmol/ml, n = 20) and normal subjects (1.0 ± 0.4 fmol/ml, n = 18) (0.05 < p < 0.1). This study has shown that high concentrations of ET-1 are present in tumor tissues of 50% of pheochromocytomas.