Binding of commercial diuretics with bovine serum albumin.

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Abstract
The binding of 7 commercial diuretics [chlorothiazide, hydrochlorothiazide, hydroflumethiazide, trichlomethazide, furosemide ethacrynic acid and bumetanide] with bovine serum albumin (BSA) was investigated at 3 different temperatures, 5.degree., 30.degree. and 37.degree. by the equilibrium dialysis method and at 37.degree. by the dynamic dialysis method. The binding data of diuretics were described on the basis that the sites per BSA molecule can be divided into 2 classes, except that of hydrochlorothiazide, and each class characterized by the binding constants, K1, n1, and K2, n2. The thermodynamic values, .DELTA.G.degree. [change in free energy], .DELTA.H.degree. (change in enthalpy) and .DELTA.S.degree. [change in entropy] for the primary site of binding were determined, and were discussed on the basis of the fact that a hydrophobic interaction is formed between diuretics and BSA. There are sizable negative entropy and enthalpy changes in the binding of ethacrynic acid and BSA; hydrochlorothiazide is bound very weakly with BSA and has a remarkable diffusion pattern through cellulose membrane in the dynamic dialysis.