Binding of bornaprolol to human serum proteins and blood cells

The binding of 14C-bornaprolol to human serum proteins and to blood cells and platelets was studied by equilibrium dialysis and centrifugation. Bornaprolol binding to alpha 1-acid glycoprotein (n = 1.89, K = 433,900 M-1) was found to be a saturable phenomenon. By contrast, a non-saturable binding was observed with serum albumin (nK = 6.4 X 10(3) M-1), HDL (nK = 205 X 10(3) M-1), LDL (nK = 1,530 X 10(3) M-1), VLDL (nK = 2,342 X 10(3) M-1) and gamma globulins (nK = 25 X 10(3) M-1). The binding to blood cells was negligible. All the binding parameters were used to simulate the distribution of bornaprolol between serum proteins and blood cells over the range of therapeutic concentrations and showed that serum albumin, red blood cells and alpha 1 acid glycoprotein were the major binding components.