Renal cortical and medullary blood flow responses to altered NO availability in humans.
The objective of this study was to quantify regional renal blood flow in humans. In nine young volunteers on a controlled diet, the lower abdomen was CT-scanned, and regional renal blood flow was determined by positron emission tomography (PET) scanning using H(2)(15)O as tracer. Measurements were performed at baseline, during constant intravenous infusion of nitric oxide (NO) donor glyceryl nitrate and after intravenous injection of NO synthase inhibitor N(ω)-monomethyl-L-arginine (L-NMMA). Using the CT image, the kidney pole areas were delineated as volumes of interest (VOI). In the data analysis, tissue layers with a thickness of one voxel were eliminated stepwise from the external surface of the VOI (voxel peeling), and the blood flow subsequently was determined in each new, reduced VOI. Blood flow in the shrinking VOIs decreased as the number of cycles of voxel peeling increased. After 4-5 cycles, blood flow was not reduced further by additional voxel peeling. This volume-insensitive flow was measured to be 2.30 ± 0.17 ml·g tissue(-1)·min(-1) during the control period; it increased during infusion of glyceryl nitrate to 2.97 ± 0.18 ml·g tissue(-1)·min(-1) (P < 0.05) and decreased after L-NMMA injection to 1.57 ± 0.17 ml·g tissue(-1)·min(-1) (P < 0.05). Cortical blood flow was 4.67 ± 0.31 ml·g tissue(-1)·min(-1) during control, unchanged by glyceryl nitrate, and decreased after L-NMMA [3.48 ± 0.23 ml·(g·min)(-1), P < 0.05]. PET/CT scanning allows identification of a renal medullary region in which the measured blood flow is 1) low, 2) independent of reduction in the VOI, and 3) reactive to changes in systemic NO supply. The technique seems to provide indices of renal medullary blood flow in humans.
Damkjær
Mads
M
Institute of Molecular Medicine, Univ. of Southern Denmark, 21 J. B. Winsloews Vej, DK-5000 Odense, Denmark.
Vafaee
Manoucher
M
Møller
Michael L
ML
Braad
Poul Erik
PE
Petersen
Henrik
H
Høilund-Carlsen
Poul Flemming
PF
Bie
Peter
P
D000704:Analysis of Variance; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006439:Hemodynamics; D006801:Humans; D007672:Kidney Cortex / Q000000981:diagnostic imaging / Q000187:drug effects*; D007679:Kidney Medulla / Q000000981:diagnostic imaging / Q000187:drug effects*; D009569:Nitric Oxide / Q000502:physiology*; D011859:Radiography; D011877:Radionuclide Imaging; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology*; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D009569:Nitric Oxide