1.
Pheochromocytoma and markers of oxidative stress.
Turková, H, Petrák, O, Skrha, J, Widimský, J, Zelinka, T
Physiological research. 2013;(3):331-5
Abstract
High levels of catecholamines in pheochromocytoma (PHEO) are associated with risk of cardiovascular complications. In this study, we looked for potential differences in markers of oxidative stress - vitamin C, superoxide dismutase (SOD) and malondialdehyde (MDA) in PHEO before and after the operation. We studied 18 subjects with PHEO who were examined before and approximately one year after the successful tumor removal (free of disease). All subjects had elevated urinary epinephrine and/or norepinephrine levels before the operation. Vitamin C levels increased significantly after the operation from 61+/-27 to 77+/-20 micromol/l (P=0.02), and MDA decreased significantly after the tumor removal from 2.6+/-0.4 to 2.0+/-0.6 micromol/l (P=0.01). However, no changes were found in SOD activity before and after the operation. In conclusion, increased catecholamine production in PHEO is accompanied by decreased levels of vitamin C and increased levels of MDA which may indicate the activation of oxidative stress in PHEO. Successful operation was associated with lowering of oxidative stress by using both biomarkers. On the contrary, no changes in SOD activity before and after the tumor removal were noted.
2.
The hemodynamic and neurohumoral phenotype of postural tachycardia syndrome.
Garland, EM, Raj, SR, Black, BK, Harris, PA, Robertson, D
Neurology. 2007;(8):790-8
Abstract
BACKGROUND Previous studies of patients with postural tachycardia syndrome (POTS) have been hampered by relatively small cohorts, failure to control medications and diet, and inconsistent testing procedures. METHODS The Vanderbilt Autonomic Dysfunction Center Database provided results of posture studies performed in 165 patients and 66 normal controls after dietary and medication restrictions. All posture studies were performed after an overnight fast and > or =30 minutes of supine rest. RESULTS In both the supine and standing positions, heart rate (HR) and plasma concentrations of norepinephrine (NE), epinephrine, and dopamine were higher in patients with POTS compared with the healthy controls. Supine diastolic blood pressure (BP) was also elevated in POTS, whereas supine plasma l-3,4-dihydroxyphenyalanine was reduced. In an analysis of patient subgroups with either an upright plasma NE > or = 3.54 nM (high NE) or an upright plasma NE < 3.54 nM (normal NE), HR and BP were greater in the patient subgroup with high NE. In addition to these significant differences in hemodynamic and catechol measurements, we demonstrated that supine and standing plasma aldosterone and the aldosterone/renin ratio were decreased in patients with POTS. Plasma renin activity (PRA) tended to be higher in patients, and standing HR for those in the highest PRA quartile was significantly greater than for those in the lowest PRA quartile. CONCLUSIONS Our results from larger cohorts of patients and controls than previously studied confirm published findings and contribute additional evidence of sympathetic activation in postural tachycardia syndrome (POTS). Abnormalities in the renin-angiotensin-aldosterone system may also contribute to the POTS phenotype.