Sympathetic nervous system overactivity in hypertensive patients with chronic renal failure--role of upright body position.
OBJECTIVE
The renal functional consequences of an activated sympathetic nervous system and plasma atrial natriuretic hormone (ANP) in various renal diseases are not well described. We hypothesize that norepinephrine (NE) and ANP have antagonizing effects on renal hemodynamics in diseased kidneys.


METHODS
Plasma NE, ANP. glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and mean arterial pressure (MAP) were measured in the upright position in healthy controls (n = 9) and hypertensive patients with reduced GFR (n =11). The same parameters were compared between healthy controls (n = 6) and hypertensive patients with reduced GFR (n = 6) in upright and supine positions.


RESULTS
Upright plasma NE and ANP were significantly elevated in the patients compared with the controls (4.4 +/- 0.4 vs 2.1 +/- 0.2 nmol/l (p < 0.001) and 1.3.5 +/- 2.1 vs 6.9 +/- 1.0 nmol/l (p < 0.01) respectively). With change from upright to supine position plasma NE decreased in the controls (2.2 +/- 0.3 vs 1.7 +/- 0.3 nmol/l) (p < 0.01) and patients (3.8 +/- 0.4 vs 2.6 +/- 0.4) (p < 0.01). Supine ANP increased in controls (5.5 +/- 1.0 vs 8.3 +/- 1.1) (p < 0.01) but not in patients (14.3 +/- 3.8 vs 16.1 +/- 3.8 nmol/l) (p > 0.10). Plasma NE correlated positively with MAP (p < 0.001) and negatively with GFR (p < 0.01) in the upright but not supine position. A positive correlation between NE and ANP was observed in upright (p < 0.001) but not in supine position. ANP correlated negatively with GFR in the upright (p < 0.01) but not supine position. No position dependent changes were seen in GFR and ERPF, but supine filtration fraction (FF) increased insignificantly in the patient group (0.23 +/- 0.02 vs 0.24 +/- 0.02) (p < 0.05).


CONCLUSIONS
Hypertensive patients with reduced GFR have elevated levels of plasma NE and ANP in the upright body position. When the upright and supine positions are compared, plasma NE declines in the supine position in controls and hypertensive renal failure patients. and plasma ANP levels are elevated only in the upright position in hypertensive renal failure patients where the sympathetic nervous system is activated. A significant positive relationship between plasma NE and ANP was observed only in the upright position. The upright body position seems superior to recumbency in the characterization of these hormonal changes in hypertensive chronic renal failure patients.
Svarstad
E
E
Renal Research Group, Institute of Medicine, University of Bergen, Norway. einar.svarstad@med.uib.no
Myking
O
O
Ofstad
J
J
Iversen
B M
BM
D009320:Atrial Natriuretic Factor / Q000097:blood; D001794:Blood Pressure; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000150:complications / Q000503:physiopathology*; D007676:Kidney Failure, Chronic / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D011187:Posture; D017596:Renal Plasma Flow, Effective; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013566:Sympathomimetics / Q000097:blood
D013566:Sympathomimetics; D009320:Atrial Natriuretic Factor; D009638:Norepinephrine