Tmdotp⁵⁻ as a ²³na shift reagent for the in vivo rat kidney

Abstract

Since transmembrane sodium gradient is essential to many cell functions, there is continuing interest in methods that differentiate intracellular and extracellular Na+. In the kidney, shift reagent (SR) aided 23Na magnetic resonance spectroscopy (MRS) has been successfully used only in isolated cells, tubules, and the perfused organ. In this report, we demonstrate for the first time that TmDOTP5- can be used to distinguish Na+ compartments in kidneys in vivo. Infusion of 80 mM TmDOTP5- without added Ca2+ produced three resolved 23Na resonances, which we have assigned to intracellular Na+, vascular Na+, and intraluminal Na+. In comparison, infusion of 400 mM DyTTHA3- produced two broad and unresolved resonances. The 31P spectra of the cellular high energy phosphate metabolites indicate that TmDOTP5- is safe for in vivo applications. Washout studies suggest that this SR displays renal clearance similar to that of MR imaging contrast agents. However, the glomerular filtration rate (GFR) in animals infused with TmDOTP5- was reduced by 49% compared with the GFR in control animals, perhaps due to the hypotensive effects of the SR. We conclude that TmDOTP5- is effectively cleared from the blood of live animals but that a different formulation will be required for clinical application.

Determination of the intracellular sodium concentration in perfused mouse liver by 31P and 23Na magnetic resonance spectroscopy

“…The Nat shift reagent, TmDOTP"., has also proven to be quite efficient in vivo for separating EC and IC 23Na NMR resonances in various organs (4)(5)(6)(7)(8). In this study, we have combined the two methods to quantify "a],, in the isolated, perfused mouse liver.…”

“…A partially saturated 3'P spectrum was acquired using a 1 s repetition delay (TR), 45" flip angle (8), and 600 scans (NA) after the stabilization period following surgery and at the end of each experiment to check the metabolic status of each liver. The concentration of hepatic ATP was determined from the relative areas of the P-ATP and MPA resonances (17).…”

Abstracts (Continue in Part XXXV)

“…By using neuronal and glial cell lines, the bioreactor may provide a simple model system for elucidating the mechanisms responsible for the cytotoxic edema observed in cerebral ischemia and could also be used to evaluate neuroprotective drugs. In addition to the NMR measurements of cell volume and energetics used in this study, measurements of membrane potential and intracellular ion concentrations could also be made [8,9].…”

In vivo23Na NMR studies of myotonic dystrophy

“…The 90° pulse width was 400 ps. Each spectrum was a result of 336 scans with line broadening of 10 Hz, a relaxation delay of 400 ms, and t, of 0.5 ms. Both legs of each patient were examined.…”

“…Paramagnetic shift reagents have been used for in vivo '"Na NMR studies of animals to distinguish between intracellular and extracellular sodium signals (8)(9)(10). However, these compounds cannot be used in human studies due to their toxicity.…”