An in vitro study of lithium index in healthy Chinese

The lithium index, a ratio of erythrocyte (intracellular) to plasma (extracellular) lithium concentrations, were studied by in vitro method in 22 healthy volunteers, 15 men and 17 women. Their mean age was 31.0 +/- 4.6 years (ranging from 26 to 41 years). In the study design, 20 ml of venous blood was taken from each subject into a test tube containing sodium citrate at the room temperature and erythrocytes were separated from plasma immediately. Then, the whole procedures for preparation and determination of lithium index were performed by using Pandey's method. Lithium levels were measured by atomic absorption spectrophotometry. Values of lithium index in vitro thus obtained were: 0.43 +/- 0.13 (range, 0.23-0.73) in men plus women; 0.37 +/- 0.10 (range, 0.23-0.57) in men; 0.49 +/- 0.13 (range, 0.26-0.73) in women. Women had a significantly higher Li+ index in vitro than men (t = 2.86, d.f. = 30, p less than 0.005). The possible reasons for the difference of the Li+ index in vitro between our result and other studies were discussed.