[The reciprocal actions of phenprocoumon (Marcumar) with human serum albumin, erythrocytes and blood]

The binding properties of phenprocoumon (PhC) to human serum albumin (HSA) and to red blood cells (RBC) were determined by using the equilibrium dialysis. Analysis of PhC-binding data to HSA at pH 7.4 and temperatures of 10 degrees C and 27 degrees C resulted in binding constants (k) of 11.8 - 10(4) and 7.0 - 10(4), in free standard enthalpy changes deltaG0 of -6.658 and -6.651 kcal/mol, and in standard enthalpy change TdeltaS0 of 1.386 and 1.469 kcal/mole, respectively. The standard enthalpy change deltaH0 was -5.182 kcal/mole for both temperatures. These results indicate that the binding between PhC and HSA is predominantly effected by hydrophobic interactions. At pH 7.4 the binding to HSA is essentially characeterized by two straight lines of binding, whereas at pH 9 and 10 there are three. With increasing pH more binding sites become free and the affinity of PhC to HSA grows. Studies of binding properties to RBC indicate a strong binding of PhC to hemoglobin (k 7.9 - 10(5)), but only a weak one to red cell membranes (binding ratio hemoglobin to ghosts 66 : 1). In a combined system of HSA and RBC, competition occurs between both components and therefore the strength of binding decreases. At therapeutic PhC-concentrations, 91.7% of the PhC are bound to the whole blood, 20.8% to RBC, and 70.9% to HSA. With increasing concentrations of PhC the binding to RBC declines to 10.5% accompanied by an approximately unchanged binding to whole blood of 92.1%; whereas binding to HSA increases to 81.6%. The affinity of PhC to HSA grows larger than its affinity to RBC. The total binding to blood remains unchanged within a 21-fold range and it is predominantly determined by the affinity of HSA to PhC.

[Rodenticidal action of warfarin/4th communication: Binding to serum albumin of mice and rats (author's transl)]

The binding properties of 3-(1'-phenyl-2'-acetylethyl)-4-hydroxycoumarine (warfarin-Na) to serum albumin of mice and rats were determined by using the equilibrium dialysis. The binding percentage (beta), the binding capacity (K), and the association constant (K1) were calculated. The results are characteristic for a strong binding of warfarin to serum albumin of rats but only a small one to serum albumin of mice, caused probably by the different albumin structures of these species.