Erythrocyte choline transport in drug-free and lithium-treated individuals

The choline (Ch) content of erythrocytes (RBCs) has been reported to be elevated in several psychiatric and neurologic disorders. The present investigation was conducted in order to examine the relationship between in vivo RBC Ch content and Ch flux across the RBC membrane (measured in vitro). To perform the in vitro studies, we measured the outward transport of endogenous Ch (DoCh efflux) and the concomitant inward transport of deuterated Ch (D4Ch influx), in RBCs that were incubated in physiologic media for 24 min at 17 degrees C. Transport of the Ch isotopes was linear during these incubations. In drug-free, psychiatrically normal control subjects, DoCh efflux was inversely correlated with the natural logarithm of in vivo RBC Ch content (r = -0.97, p less than 0.001), and there was a nearly significant correlation between D4Ch influx and in in vivo RBC Ch content (r = -0.81, p less than 0.06). In patients with bipolar affective disorder, lithium treatment both inhibited DoCh and D4Ch transport, and substantially elevated in vivo RBC Ch content. However, varying degrees of transport inhibition were produced by this drug in different subjects. Our findings suggest that membrane Ch transport may have a role in the regulation of endogenous RBC Ch content. Studies of membrane Ch transport in RBCs or other types of cells could potentially help to increase our understanding of cholinergic function in psychiatric or neurologic disorders.