LITHIUM DISTRIBUTION IN RED-BLOOD-CELLS AND PLASMA - NMR-STUDIES OF RAT-BLOOD

To understand the interaction of lithium (Li+) with a coadministered d rug in both the blood and the brain, we have treated rats with either Li+ alone or Li+ and a codrug. In this paper we address the important problem of quantitation of intra and extracellular Li+ ion contents in blood by the Li-7-NMR technique and the use of a shift reagent (SR). Although Li+ can be studied by atomic absorption techniques, these tec hniques involve tedious separation of intra-and extracellular componen ts prior to chemical analysis, Magnetic resonance studies on rat blood , in the dose range of 0.5 to 10 meq/kg, indicate that the intracellul ar red blood cell Li+ predominates in the lower dose range of 0.5-1.0 meq/kg, As the lithium dose increases, a significantly larger amount o f Li+ accumulates in the extracellular volume, Our studies on a number of animals at various doses of LiCl indicate that Li-7-NMR of blood s amples provide a reliable, noninvasive quantification of red blood cel l and plasma Li+ concentrations, The NMR method was further used to st udy the effect of coadministered drugs such as thioridazine on the int ra-and extracellular Li+ concentration of RBCs. (C) 1998 Elsevier Scie nce Inc.