Binding of tubocurarine to specific serum protein fractions

The binding of tritium-labelled tubocurarine to separate protein fractions of sera from normal subjects and patients with hepatic disease was measured by an electrophoretic technique. The binding of the drug to gamma globulin and albumin solutions also was studied using equilibrium dialysis. The major portion of the drug, 82-90%, was bound to the gamma globulin electrophoretic fraction of both normal and patient sera. However, as measured by equilibrium dialysis, only 15.8% of the drug was bound to the gamma globulin and 23.8% to albumin. Equilibrium dialysis yields the data by which the validity of other methods for measuring drug-protein binding can be judged. Since in a previous study we also found no difference in binding of the drug between healthy individuals and patients with hepatic disease, equilibrium dialysis measurements may reflect better the binding of the drug in vivo.