title: Magnetic Resonance Imaging-Derived Renal Oxygenation and Perfusion During Continuous, Steady-State Angiotensin-II Infusion in Healthy Humans.
abstract: BACKGROUND
  The role of kidney hypoxia is considered pivotal in the progression of chronic kidney disease. A widely used method to assess kidney oxygenation is blood oxygen level dependent (BOLD)-magnetic resonance imaging (MRI), but its interpretation remains problematic. The BOLD-MRI signal is the result of kidney oxygen consumption (a proxy of glomerular filtration) and supply (ie, glomerular perfusion). Therefore, we hypothesized that with pharmacological modulation of kidney blood flow, renal oxygenation, as assessed by BOLD-MRI, correlates to filtration fraction (ie, glomerular filtration rate/effective renal plasma flow) in healthy humans.
  
  
  RESULTS
  Eight healthy volunteers were subjected to continuous angiotensin-II infusion at 0.3, 0.9, and 3.0 ng/kg per minute. At each dose, renal oxygenation and blood flow were assessed using BOLD and phase-contrast MRI. Subsequently, "gold standard" glomerular filtration rate/effective renal plasma flow measurements were performed under the same conditions. Renal plasma flow decreased dose dependently from 660±146 to 467±103 mL/min per 1.73 m(2) (F[3, 21]=33.3, P<0.001). Glomerular filtration rate decreased from 121±23 to 110±18 mL/min per 1.73 m(2) (F[1.8, 2.4]=6.4, P=0.013). Cortical transverse relaxation rate (R2*; increases in R2* represent decreases in oxygenation) increased by 7.2±3.8% (F[3, 21]=7.37, P=0.001); medullar R2* did not change. Cortical R2* related to filtration fraction (R(2) 0.46, P<0.001).
  
  
  CONCLUSIONS
  By direct comparison between "gold standard" kidney function measurements and BOLD MRI, we showed that cortical oxygenation measured by BOLD MRI relates poorly to glomerular filtration rate but is associated with filtration fraction. For future studies, there may be a need to include renal plasma flow measurements when employing renal BOLD-MRI.
authors.affiliation: Department of Internal Medicine, Academic Medical Center at the University of Amsterdam, The Netherlands.
authors.forename: René
authors.initials: R
authors.lastname: van der Bel
authors.affiliation: Department of Radiology, Academic Medical Center at the University of Amsterdam, The Netherlands.
authors.forename: Bram F
authors.initials: BF
authors.lastname: Coolen
authors.affiliation: Department of Radiology, Academic Medical Center at the University of Amsterdam, The Netherlands.
authors.forename: Aart J
authors.initials: AJ
authors.lastname: Nederveen
authors.affiliation: Department of Radiology, Academic Medical Center at the University of Amsterdam, The Netherlands.
authors.forename: Wouter V
authors.initials: WV
authors.lastname: Potters
authors.affiliation: Department of Nuclear Medicine, Academic Medical Center at the University of Amsterdam, The Netherlands.
authors.forename: Hein J
authors.initials: HJ
authors.lastname: Verberne
authors.affiliation: Department of Internal Medicine, Academic Medical Center at the University of Amsterdam, The Netherlands.
authors.forename: Liffert
authors.initials: L
authors.lastname: Vogt
authors.affiliation: Department of Internal Medicine, Academic Medical Center at the University of Amsterdam, The Netherlands.
authors.forename: Erik S G
authors.initials: ES
authors.lastname: Stroes
authors.affiliation: Department of Internal Medicine, Academic Medical Center at the University of Amsterdam, The Netherlands c.t.krediet@amc.uva.nl.
authors.forename: C T Paul
authors.initials: CT
authors.lastname: Krediet
mesh_terms: D000804:Angiotensin II / Q000008:administration & dosage*; D015415:Biomarkers / Q000097:blood; D004305:Dose-Response Relationship, Drug; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects; D064368:Healthy Volunteers; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology; D007668:Kidney / Q000098:blood supply / Q000187:drug effects* / Q000378:metabolism; D007677:Kidney Function Tests / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000187:drug effects*; D055420:Perfusion Imaging / Q000379:methods*; D011237:Predictive Value of Tests; D012079:Renal Circulation / Q000187:drug effects*; D017596:Renal Plasma Flow, Effective / Q000187:drug effects; D015203:Reproducibility of Results; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D010100:Oxygen
keywords: blood oxygen level–dependent; chronic kidney disease; magnetic resonance imaging; renal oxygenation; renal perfusion; renin angiotensin system