Calmodulin-activated calcium ATPase in bipolar illness.

Calmodulin-activated calcium ATPase is a transport enzyme which establishes the normal level of intracellular ionized calcium in most cells. We have determined values for three parameters of this enzyme: E-t, the concentration in the membrane; Vmax, the maximal velocity, and Ka, the binding affinity for calmodulin. We assayed these parameters in erythrocyte membranes from lithium carbonate-treated bipolar subjects and from normal controls. Bipolar subjects have significantly increased levels of E-t compared with normal controls.