title: On the use of 133Cs as an NMR active probe of intracellular space in vivo.
abstract: Data are presented from 133Cs NMR studies on both excised and in situ tissues from rats fed a regular diet and administered i.p. CsCI in aqueous solution for 6 to 14 days. Cesium is an NMR-active potassium analog which accumulates in the intracellular spaces of tissues [Davies et al., Biochemistry 27, 3547 (1988); Shehan, B.P. et al., Magn. Reson. Med. 30,573 (1993)]. Chemical shifts, relaxation properties, sensitivity and detectability of cesium in tissues were investigated. Consistent with previous reports, two resonances (representing intra- and extracellular cesium) were detected in blood. Only one resonance was detected in brain, kidney, and muscle tissue. Efforts to resolve intra- and extracellular components by T1 and T2 relaxation discrimination were not successful. Following i.p. administration, cesium accumulates intracellularly with a brain-to-cerebrospinal fluid concentration (mumol/g) ratio of 9:1 and a thigh muscle-to-plasma concentration ratio of 40:1. Considering the small extracellular volume in these tissues (ca 18% and 10%, respectively), the net content differences between intra- and extracellular cesium are approximately 40-fold in brain and 360-fold in muscle. The concentration ratio of cesium in brain to cesium in cerebrosinal fluid decreased to 3:1 1 h after death, indicating a relatively slow rate of leakage of cesium from the intra- to extracellular space in the face of bioenergetic failure. These data suggest that the cesium signal is dominated by the intracellularly located cesium and, thus, cesium may be useful as a probe of the intracellular environment despite an inability to resolve and directly observe distinct resonances from intra- and extracellular spaces.
authors.affiliation: Department of Chemistry, Washington University, St Louis, MO 63130-4899, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: J
authors.initials: J
authors.lastname: Neil
authors.forename: J J
authors.initials: JJ
authors.lastname: Ackerman
mesh_terms: D000818:Animals; D002586:Cesium / Q000032:analysis / Q000493:pharmacokinetics*; D002587:Cesium Isotopes; D005240:Feasibility Studies; D007424:Intracellular Fluid / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D002587:Cesium Isotopes; D002586:Cesium