Binding of lithium and boron to human plasma proteins

The binding of lithium and boron, at normal physiological levels, to plasma proteins has been investigated by the techniques of precipitation with eth yl alcohol and gel chromatography. Assays of lithium and boron were made by thermal neutron activation and mass spectrometric assay of He-3 and He-4. Results of alcohol precipitation experiments for plasma from two apparently healthy donors showed that 13 +/- 4% and 16 +/- 3% of the lithium in plasm a is protein bound, but essentially no boron is bound under the conditions used. We believe that because of denaturation of proteins which occurs duri ng alcohol precipitation, these percentages represent lithium and boron tig htly bound to protein molecules. The results of the gel-chromatography expe riment, on the other hand, showed that lithium and boron are bound to a wid e range of plasma proteins, from low (similar to 60,000 amu) to high (simil ar to 1,000,000 amu) molecular weights, and to very low- (similar to 6000 a mu) molecular-weight ligands. Although a clear identification of the specif ic proteins which bind lithium and boron cannot be made at present, some po ssibilities can be suggested.