Erythrocyte glycine in depressed, hypomanic, and euthymic bipolar patients treated with lithium carbonate.

Red blood cell (RBC) glycine levels were examined in 27 bipolar patients, treated with lithium carbonate for a minimum of 8 months, who were either hypomanic, depressed, or euthymic in their mood. We found no difference in the RBC glycine or in the RBC: plasma glycine ratio between the hypomanic, depressed, or euthymic patients (P less than 0.1). There were statistically significant differences in RBC glycine levels in lithium-treated euthymic patients and normal controls. There was a strong positive correlation between serum lithium levels and both RBC glycine levels and the RBC: plasma glycine ratio.