Journal
HYPERTENSION
Volume 55, Issue 5, Pages 1116-1122Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/HYPERTENSIONAHA.109.149682
Keywords
BOLD-MRI; hypertension; sodium; renal tissue oxygenation; proximal tubule; medulla; inulin clearance
Categories
Funding
- Swiss Renal Foundation
- Hypertension Research Foundation
- Swiss National Science Foundation [FN 33CM30-124087, FN 3100AO-120406]
- Centre D'imagerie Biomedicale of the University of Lausanne
- Swiss Federal Institute of Technology Lausanne
- University of Geneva
- Centre Hospitalier Universitaire Vaudois
- Hopitaux Universitaires de Geneve
- Leenaards foundation
- Jeantet foundation
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The goal of this study was to investigate the effect of sodium intake on renal tissue oxygenation in humans. To this purpose, we measured renal hemodynamics, renal sodium handling, and renal oxygenation in normotensive (NT) and hypertensive (HT) subjects after 1 week of a high-sodium and 1 week of a low-sodium diet. Renal oxygenation was measured using blood oxygen level dependent magnetic resonance. Tissue oxygenation was determined by the measurement of R2* maps on 4 coronal slices covering both kidneys. The mean R2* values in the medulla and cortex were calculated, with a low R2* indicating a high tissue oxygenation. Ten male NT (mean age: 26.5 +/- 7.4 years) and 8 matched HT subjects (mean age: 28.8 +/- 5.7 years) were studied. Cortical R2* was not different under the 2 conditions of salt intake. Medullary R2* was significantly lower under low sodium than high sodium in both NT and HT subjects (28.1 +/- 0.8 versus 31.3 +/- 0.6 s(-1); P<0.05 in NT; and 27.9 +/- 1.5 versus 30.3 +/- 0.8 s(-1); P<0.05, in HT), indicating higher medullary oxygenation under low-sodium conditions, In NT subjects, medullary oxygenation was positively correlated with proximal reabsorption of sodium and negatively with absolute distal sodium reabsorption, but not with renal plasma flow. In HT subjects, medullary oxygenation correlated with the 24-hour sodium excretion but not with proximal or with the distal handling of sodium, These data demonstrate that dietary sodium intake influences renal tissue oxygenation, low sodium intake leading to an increased renal medullary oxygenation both in nonnotensive and young hypertensive subjects. (Hypertension. 2010;55:1116-1122.)
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