Measurement of lithium transport in RBC from psychiatric patients receiving lithium carbonate and normal individuals by 7Li NMR spectroscopy

Applications of (7)Li NMR in biomedicine

The applications of (7)Li NMR spectroscopy and imaging in biology and experimental medicine have been progressing steadily. The interest derives primarily from the clinical use of Li salts to treat mania and manic-depressive illness. One area of investigation is ionic transport across the cellular membrane and compartmentation, so as to elucidate the mechanism(s) of therapeutic action and toxicity in clinical practice. The second is the development of a noninvasive, in vivo analytical tool to measure brain Li concentrations in humans, both as an adjunct to treatment and as a mechanistic probe. Here we review progress to date in this area.

Competition between Li+ and Mg2+ for red blood cell membrane phospholipids: A 31P, 7Li, and 6Li nuclear magnetic resonance study

The mode of action of the lithium ion (Li+) in the treatment of manic depression or bipolar illness is still under investigation, although this inorganic drug has been in clinical use for 50 yr. Several research reports have provided evidence for Li+/Mg2+ competition in biomolecules. We carried out this study to characterize the interactions of Li+ and Mg2+ with red blood cell (RBC) membrane components to see whether Li+/Mg2+ competition occurs. 31P nuclear magnetic resonance chemical shift measurements of the phospholipids extracted from the RBC membranes indicated that the anionic phospholipids, phosphatidylserine and phosphatidylinositol, bind Li+ and Mg2+ most strongly. From 6Li relaxation measurements, the Li+ binding constant to the phospholipid extract was found to be 45 +/- 5 M(-1). Thus, these studies showed that the phospholipids play a major role in metal ion binding. 7Li spin-lattice relaxation measurements conducted on unsealed and cytoskeleton-depleted RBC membrane in the presence of magnesium indicated that the removal of the cytoskeleton increases lithium binding to the more exposed anionic phospholipids (357 +/- 24 M(-1)) when compared to lithium binding in the unsealed RBC membrane (221 +/- 21 M(-1)). Therefore, it can be seen that the cytoskeleton does not play a major role in Li+ binding or in Li+/Mg2+ competition.

The uptake of Li+ into human 1321 N1 astrocytomas using 7Li NMR spectroscopy

The uptake of Li+ ions into human 1321 N1 astrocytomas cultured on the surface of microcarrier beads was followed by 7Li NMR spectroscopy. The intracellular and extracellular 7Li resonances were separated by the use of dysprosium tripolyphosphate as a shift reagent. Excellent spectra were obtained from which the uptake of Li+ was found to be approximately ten times faster than that into human erythrocytes using the same technique and a steady-state intracellular Li+ concentration was observed within 60 min. The low intracellular Li+ concentration attained, relative to the extracellular concentration, indicates the presence of an efflux mechanism in astrocytomas that actively transports Li+ against its concentration gradient. The intracellular volume was estimated by quantitative 23Na NMR spectroscopy and the viability of the cells was confirmed by 31P NMR spectroscopy.

The effect of lithium therapy upon the composition of the human erythrocyte membrane

The membrane phospholipids and membrane proteins from the erythrocytes of manic depressive patients undergoing lithium therapy and of normal controls were examined by high performance TLC and gel electrophoresis, respectively. The phospholipid composition of the erythrocyte membranes of the normal controls was close to that reported previously. The lipid composition of the erythrocyte membranes of the patients was very similar but differed from the normal controls in that the proportion of sphingomyelin and cholesterol appeared to be lower, whereas phosphatidylserine appeared to be higher in the patients by amounts comparable with the sums of the 95% confidence limits on the measurements. No major differences in the protein composition of the erythrocyte membranes were detected.

The effect of short term lithium treatment on the leukocyte, liver and muscle carbohydrate metabolism of guinea-pigs

1. The effect of lithium treatment on the leukocyte, liver and muscle glycogen levels of guinea-pigs has been studied. 2. A 4-week treatment with lithium chloride (5 mmol/l i.p. in saline) increased leukocyte, liver and muscle glycogen and decreased blood glucose levels. 3. These results strongly suggest that a lithium-induced insulin-like effect may be related to the long term effect.

Reinvestigation of the transmembrane difference in 7Li NMR T1 values in Li(+)-loaded human erythrocyte suspensions

In contrast to the findings in a recent study (R. P. Gullapalli, R. M. Hawk, R. A. Komoroski, Magn. Reson. Med. 20, 240 (1991)), we found that, even at high hematocrits, the T1 values for extracellular 7Li were at least three times longer than those for intracellular Li+. We conclude that a transmembrane difference in T1 values can be used for separate observation of intracellular and extracellular Li+ in human red blood cell suspensions.

Effect of lithium on the double-quantum behavior of 23Na in normal human erythrocytes

The double-quantum behavior of 23Na in the presence of different concentrations of Li in human erythrocytes was investigated. The 23Na double-quantum signal was quenched in both the extracellular and the intracellular compartments with increasing concentration of Li in each compartment, along with an increase in the 23Na T1 both intra- and extracellularly. Some extracellular quenching could be observed at the near therapeutic concentration of 2 mM Li. The ratio of slow to fast spin-spin (T2) relaxation times, obtained from the dependence of the double-quantum signal on creation time, approached unity at an overall Li concentration of 40 mM. These results provide evidence that Li and Na compete for both intra- and extracellular binding sites in erythrocytes.