Lymphoblastoid transmembrane potential in bipolar patients, their siblings, and unrelated healthy comparison subjects

Bipolar illness appears to be characterized by alterations in ionic homeostasis that are related to mood state. This is reflected by reports of altered intracellular sodium and calcium concentrations, altered sodium pump (Na+,K+-adenosine triphosphatase), and calcium pump (Ca2+-adenosine triphosphatase) activity. Recent ex vivo studies with fresh lymphocytes and in vitro studies with cultured lymphoblasts suggest that there may be an enduring trait-related abnormality in Na+,K+-adenosine triphosphatase as well. We have previously found that the lymphocyte transmembrane potential (TMP) varies with mood state. To examine the question of trait-related changes in TMP, we studied TMP of immortalized lymphoblasts from 14 patients with bipolar illness, nine unaffected siblings, and eight normal subjects. TMP was the same in all three groups. These preliminary data suggest that TMP is a state-- rather than a trait-related marker.