Renal oxygen content is increased in healthy subjects after angiotensin-converting enzyme inhibition.
OBJECTIVE
The association between renal hypoxia and the development of renal injury is well established. However, no adequate method currently exists to non-invasively measure functional changes in renal oxygenation in normal and injured patients.


METHODS
R2* quantification was performed using renal blood oxygen level-dependent properties. Five healthy normotensive women (50 ± 5.3 years) underwent magnetic resonance imaging in a 1.5T Signa Excite HDx scanner (GE Healthcare, Waukesha, WI). A multiple fast gradient-echo sequence was used to acquire R2*/T2* images (sixteen echoes from 2.1 ms/slice to 49.6 ms/slice in a single breath hold per location). The images were post-processed to generate R2* maps for quantification. Data were recorded before and at 30 minutes after the oral administration of an angiotensin II-converting enzyme inhibitor (captopril, 25 mg). The results were compared using an ANOVA for repeated measurements (mean + standard deviation) followed by the Tukey test. ClinicalTrials.gov: NCT01545479.


RESULTS
A significant difference (p<0.001) in renal oxygenation (R2*) was observed in the cortex and medulla before and after captopril administration: right kidney, cortex = 11.08 ± 0.56 ms, medulla = 17.21 ± 1.47 ms and cortex = 10.30 ± 0.44 ms, medulla = 16.06 ± 1.74 ms, respectively; and left kidney, cortex= 11.79 ± 1.85 ms, medulla = 17.03 ± 0.88 ms and cortex = 10.89 ± 0.91 ms, medulla = 16.43 ± 1.49 ms, respectively.


CONCLUSIONS
This result suggests that the technique efficiently measured alterations in renal blood oxygenation after angiotensin II-converting enzyme inhibition and that it may provide a new strategy for identifying the early stages of renal disease and perhaps new therapeutic targets.
Fundação Universitária de Cardiologia (IC/FUC), Instituto de Cardiologia do Rio Grande do Sul, Porto Alegre/RS, Brazil. steinanna87@gmail.com
Anna
A
Stein
Silvia
S
Goldmeier
Sarah
S
Voltolini
Enio
E
Setogutti
Carlos
C
Feldman
Eduardo
E
Figueiredo
Renato
R
Eick
Maria
M
Irigoyen
Katya
K
Rigatto
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D002216:Captopril / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007668:Kidney / Q000098:blood supply / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D010100:Oxygen / Q000097:blood / Q000378:metabolism*; D013997:Time Factors
D000806:Angiotensin-Converting Enzyme Inhibitors; D002216:Captopril; D010100:Oxygen