7Li NMR of Normal Human Erythrocytes

Lithium has been known to be an effective medication forpeople withbipolar disorder. The mechanisms of action of lithium in the brain isnot very well understood. NMR spectroscopy and imaging are effective both in determining lithium levels in tissue and brain. We have monitored lithium levels in red blood cells. We have been able to separate intraand extracellular compartments oflithium using shift reagents, thereby obtaining T1's of both the compartments. Lithium uptake as a function of hematocrit was monitored weeklyover a 3 week period. The time constant of 50 mM lithium uptake at 25°C and 85% hematocrit was found to be 16.5 hrs. The time constant of 1.8 mM lithium uptake at 37 °C and 45% hematocrit was found to be 1 1 .6 hrs. Experiments on the visibility of the quadrupolar nuclei indicate that itis only 74-90% visible and the visibility decreased with decreasing concentrations.