NMR relaxation characteristics of rubidium-87 in perfused rat salivary glands.
Rubidium is a good substitute for potassium in many biological systems, and it has been suggested that rubidium-87 nuclear magnetic resonance (87Rb-NMR) spectroscopy could be used to measure K+ fluxes across membranes in intact tissues. To evaluate this possibility, isolated rat mandibular salivary glands were perfused with solutions containing Rb+ in place of K+. The 87Rb signals arising from the intra- and extracellular compartments were first separated by spectral subtraction and then subjected to line-shape analysis. The narrow extracellular signal was a single Lorentzian (line-width 156 Hz), whereas the broader intracellular signal consisted of two Lorentzian components (ca. 530 and 3080 Hz). Double-quantum filtering of the 87Rb signal from the glands revealed two components of transverse relaxation in antiphase (rate constants 1.8 and 13.3 ms-1), showing the probable involvement of quadrupolar interactions in the relaxation of intracellular Rb+. We conclude, therefore, that both line-shape analysis and double-quantum filtering could provide a basis for the measurement of unidirectional K+ fluxes in intact tissues.
Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Japan.
M C
MC
Steward
Y
Y
Seo
M
M
Murakami
H
H
Watari
D000818:Animals; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism*; D012414:Rubidium Radioisotopes; D013363:Submandibular Gland / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors
D012414:Rubidium Radioisotopes; D012413:Rubidium; D011188:Potassium