Dynamic renal function testing by compartmental analysis: assessment of renal functional reserve in essential hypertension.
BACKGROUND
In essential hypertension, acute haemodynamic changes due to dietary protein load cause patterns of acute changes in renal function that are fundamentally different from changes in normal controls.


METHODS
Renal clearances of sinistrin, an inulin-like polyfructosan, and p-aminohippurate were determined before and after protein ingestion. These tests were performed in healthy controls and in patients with essential hypertension (mean arterial pressure of 112+/-2 mmHg, age, 52+/-2 years; mean+/-SEM) within a washout period, and after long-term treatment with carvedilol and fosinopril, respectively.


RESULTS
In 15 healthy volunteers, protein ingestion increased glomerular filtration rate (GFR) from 110.3+/-3.6 to 120. 6+/-4.4 ml/min (P=0.0006; two-tailed pairwise t-test). In contrast, it led to an acute decrease in GFR in 16 hypertensive patients, from 111.8+/-2.9 to 103.6+/-3.3 ml/min (P=0.0010). The eight patients who were randomized to receive carvedilol improved in their renal response to protein (GFR increased from 101.4+/-6.4 to 107.1+/-5.4 ml/min; P=0.04), whereas the eight other patients randomized to receive fosinopril exhibited no change in GFR (final value 105+/-4.9 ml/min). In the patients, the acute shifts in renal plasma flows were not significant. Mean arterial blood pressure of the patients decreased from 112+/-2 to 100+/-3 mmHg (P=0.0015).


CONCLUSIONS
In essential hypertension an acute protein load induces a decrease in GFR that may normalize under antihypertensive treatment. The acute changes in GFR can be reliably monitored by the here-described compartmental analysis method of renal functional reserve.
Department of Internal Medicine, Division of Nephrology, University of Graz, Austria.
S
S
Zitta
K
K
Stoschitzky
R
R
Zweiker
K
K
Oettl
G
G
Reibnegger
H
H
Holzer
W
W
Estelberger
D000328:Adult; D000959:Antihypertensive Agents / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects; D002227:Carbazoles / Q000627:therapeutic use; D000077261:Carvedilol; D004044:Dietary Proteins / Q000494:pharmacology; D005260:Female; D017328:Fosinopril / Q000627:therapeutic use; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000188:drug therapy / Q000503:physiopathology*; D007668:Kidney / Q000378:metabolism / Q000503:physiopathology*; D007677:Kidney Function Tests / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009844:Oligosaccharides / Q000378:metabolism; D011412:Propanolamines / Q000627:therapeutic use; D012016:Reference Values; D012079:Renal Circulation / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects; D010130:p-Aminohippuric Acid / Q000378:metabolism
D000959:Antihypertensive Agents; D002227:Carbazoles; D004044:Dietary Proteins; D009844:Oligosaccharides; D011412:Propanolamines; D000077261:Carvedilol; D017328:Fosinopril; D010130:p-Aminohippuric Acid; C064636:sinistrin