RBC membrane adenosine triphosphatase activities in patients with major affective disorders

Red blood cell Na+, K+-, Mg2+-, and Ca2+-adenosine triphosphatase (ATPase) activities were studied longitudinally in eight patients with affective disorders and 12 healthy volunteers. The patients had a higher mean Ca2+-ATPase activity than the volunteers, and the fluctuations in all three ATPase activities were greater in the patients than in the volunteers. Even though the mean Ca2+-ATPase activity was higher during manias and euthymic periods than during depressions, mood and ATPase activities did not correlate with each other in all patients. Lithium carbonate treatment did not alter the ATPase activities, and the quantity of vanadium present in the membranes could not account for the variations in the enzyme activities observed. We suggest that either the RBCs of manic-depressive patients are very sensitive to fluctuations of a lipophilic ATPase activity--regulating factor present in plasma or the patients have at times high levels of such a factor. In some patients, the level of this hypothesized regulator may fluctuate in synchrony with mood changes.