title: Renal BOLD-MRI relates to kidney function and activity of the renin-angiotensin-aldosterone system in hypertensive patients.
abstract: BACKGROUND
  The renin-angiotensin-aldosterone system (RAAS) and the sympathetic nervous system are key factors in the pathophysiology of hypertension. Renal hypoxia is the putative mechanism stimulating both systems. Blood oxygen level-dependent MRI (BOLD-MRI) provides a noninvasive tool to determine renal oxygenation in humans. The aim of the current study was to investigate the relation between blood pressure (BP) and kidney function with renal BOLD-MRI. Moreover, the relation between direct and indirect variables of the RAAS and sympathetic nervous system and renal BOLD-MRI was studied.
  
  
  METHODS
  Seventy-five hypertensive patients (38 men) were included. Antihypertensive medication was temporarily stopped. Patients collected urine during 24 h (sodium, catecholamines), blood samples were taken (creatinine, renin, aldosterone), a captopril challenge test was performed, and ambulatory BP was measured.
  
  
  RESULTS
  Mean age was 58 (±11) years, day-time BP was 167 (±19)/102 (±16) mmHg, and estimated glomerular filtration rate was 75 (±18) ml/min per 1.73 m). In multivariable regression analysis, renal medullary R2*-values inversely related to estimated glomerular filtration rate (P = 0.02). Moreover, the BP-lowering effect of captopril positively related to cortical (P = 0.02) and medullary (P = 0.008) R2*-values, as well as to P90 (P = 0.02).
  
  
  CONCLUSIONS
  In patients with hypertension, kidney function relates to medullary R2*-values. Activation of the RAAS is also positively related to the renal R2*-values.
authors.affiliation: aDepartment of Nephrology and Hypertension bDepartment of Radiology cDepartment of Cardiology dJulius Center for Health Sciences and Primary Care, UMC Utrecht, The Netherlands.
authors.forename: Eva E
authors.initials: EE
authors.lastname: Vink
authors.forename: Anneloes
authors.initials: A
authors.lastname: de Boer
authors.forename: Hans J M
authors.initials: HJ
authors.lastname: Hoogduin
authors.forename: Michiel
authors.initials: M
authors.lastname: Voskuil
authors.forename: Tim
authors.initials: T
authors.lastname: Leiner
authors.forename: Michiel L
authors.initials: ML
authors.lastname: Bots
authors.forename: Jaap A
authors.initials: JA
authors.lastname: Joles
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Blankestijn
mesh_terms: D000368:Aged; D000450:Aldosterone / Q000378:metabolism; D001794:Blood Pressure / Q000502:physiology*; D003404:Creatinine / Q000378:metabolism; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D007668:Kidney / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System / Q000502:physiology*; D012964:Sodium / Q000378:metabolism
chemical_list: D000450:Aldosterone; D012964:Sodium; D003404:Creatinine; D012083:Renin