The influx of [14C] ‐choline and the efflux of 22Na in human erythrocytes were measured in vitro using blood from patients treated with lithium, patients not on lithium and healthy individuals.
The administration of lithium to patients significantly reduces the transport of choline; during the first 6 weeks of treatment the influx of choline is about half the normal rate, later it falls to around 10%.
This inhibition of choline transport is not dependent on the presence of lithium in the incubation medium. 4 The active and passive efflux of sodium are apparently not affected by lithium treatment.
1Lithium administration to patients leads to a pronounced inhibition (about 90%) of the choline transport system in erythrocytes. The transport system does not recover when ghosts are prepared from the erythrocytes, thereby removing intracellular as well as extracellular lithium. 2 When a patient is taken off lithium, the choline transport in erythrocytes recovers only very slowly over a period of three months, i.e. at about the same rate at which the erythrocytes that had been exposed to lithium are replaced by new cells. 3 It is concluded that therapeutic concentrations of lithium produce an irreversible inhibition of the choline transport system in human erythrocytes.
Soluble proteins have been obtained from squid retinal axon membrane preparations. By the use of a high concentration of iodide (I-) or thiocyanate (SCN-), proteins were solubilized containing less than 5 % of the original membrane lipids. These proteins according to their behavior in vacuum filtration, can be divided into high and low molecular weight proteins. They have been partially characterized by exclusion column chromatography, polyacrylamide gel electrophoresis, gradient eentrifugation, and analytical ultracentrifugation. They show some tendency toward reaggregation in the absence of sodium dodecyl sulfate (SDS).The soluble proteins do not show any activity of membrane enzymes and this activity was not recovered upon the incubation with membrane liposomes. Only with CIsolubilized preparations was some enzymatic activity observed.The amino acid composition of both families of proteins was obtained. The high molecular weight proteins are similar to other plasma membranes. The amount of basic amino acids in the low molecular weight proteins was significantly greater than in the high molecular weight fraction.The axolemma-rich membranes ("light membranes") were isolated from the Schwann cell membranes and the protein solubilized by SDS. By sucrose gradient centrifugation a unique protein band was found in the '~ axolemma" proteins.The relationship of the presence of unusual proteins and phospholipids with polyenoic chains is discussed with regard to the molecular organization of an excitable membrane.In 1967 our group developed a procedure for the isolation and purification of plasma membranes from retinal axon in amounts sufficient for biochemical studies [13,14]. Because of the particular ultrastructural arrangement of the retinal axons of the squid, the axolemma prevails over the "Schwannlemma" assuring adequate material to obtain nerve membranes. Further investigations made it possible to characterize rather extensively the enzymes, ultrastructure, and lipidic organization of the axolemma preparation [6, 32]. 21 J. Membrane Biol. 12
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