Sodium magnetic resonance imaging of diuresis: spatial and kinetic response.
Renal function is highly correlated with the sodium concentration gradient along the corticomedullary axis. The application of 3D high-resolution sodium magnetic resonance imaging (MRI) provided a means to quantify in vivo the spatial and temporal changes in renal tissue sodium concentration under normal and diuretic conditions. A detailed, pixel-by-pixel analysis of the intact rat kidney sodium MR images yielded a quantitative measure of the corticomedullary sodium gradient before and at early and later times after the administration of two distinct diuretic agents, furosemide and mannitol. Furosemide, a loop diuretic, induced a fivefold reduction in the cortical-outer medullary sodium gradient, whereas mannitol, an osmotic diuretic, did not affect this gradient. Both diuretics induced a 50% decrease in the sodium concentration of the inner medulla; however, mannitol exerted its effect twice as fast as furosemide with a 2.5-min exponential decay constant. These specific changes were attributed to the different mechanism of action and site of activity of each diuretic agent. Thus, high-resolution (23)Na MRI offers a unique, noninvasive tool for functional imaging of the kidney physiology.
Maril
Nimrod
N
Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel.
Margalit
Raanan
R
Mispelter
Joel
J
Degani
Hadassa
H
D000704:Analysis of Variance; D000818:Animals; D004231:Diuresis / Q000187:drug effects / Q000502:physiology*; D004232:Diuretics / Q000494:pharmacology*; D005260:Female; D005665:Furosemide / Q000494:pharmacology; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000187:drug effects*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008353:Mannitol / Q000494:pharmacology; D051381:Rats; D011917:Rats, Inbred Lew; D012964:Sodium / Q000378:metabolism*
D004232:Diuretics; D008353:Mannitol; D005665:Furosemide; D012964:Sodium