ELEVATED IMMUNOREACTIVE ENDOTHELIN LEVELS IN PATIENTS WITH PHEOCHROMOCYTOMA

Plasma immunoreactive endothelin-1 (ET-1) concentrations were measured in 44 patients with pheochromocytoma, 31 patients with essential hypertension, and 20 healthy control subjects. Plasma ET-1 concentrations in patients with pheochromocytoma were 18.2 +/- 3.2 fmol/mL (mean +/- SEM), which was significantly higher than those of essential hypertension and healthy Control subjects (7.3 +/- 0.4, 7.1 +/- 0.4 fmol/mL, respectively, P < .01). Plasma ET-1 concentrations in patients with essential hypertension and control subjects were similar. In patients with pheochromocytoma, hypertensive group had higher ET-1 than normotensive group (23.0 +/-: 5.5 v 12.4 +/- 2.2 fmol/mL), but the difference was not significant. In 17 patients with pheochromocytoma, the elevated plasma ET-1 concentrations (17.4 +/- 4.7 fmol/mL,) returned to normal levels (7.9 +/- 0.6 fmol/mL, P < .05) after surgical resection of the tumor. ET-1 contents in the 26 tumor tissues (1.40 +/- 0.29 pmol/g) were higher than those in 7 normal adrenal medullas (0.44 +/- 0.12 pmol/g). Systolic, diastolic, and mean blood pressures were better correlated with plasma norepinephrine than ET-1 in patients with pheochromocytoma. These data indicate that pheochromocytoma might produce and secrete excessive amounts of ET-1. The hypertension in patients with pheochromocytoma is mainly catecholamine-dependent, but may be secondarily ET-1-dependent.