Effect of free fatty acid concentration on furosemide binding to human serum albumin.

The effect of varying concentrations of sodium oleate on the binding of furosemide to human serum albumin was investigated using continuous ultrafiltration. The furosemide fraction free was 1.37% in the absence of sodium oleate increasing to 3.52% in the presence of 2 mEq/l of sodium oleate. Furosemide bound to two types of binding sites on the albumin molecule. It was found that the numbers of binding sites of each type were constant with the addition of free fatty acid (FFA); however, the decrease in the affinity constants for each site was directly proportional to the increase in FFA over the range of 0-2 mEq/l added sodium oleate. Sodium palmitate and linoleic acid were tested individually to determine the effect of interaction, the fraction free increasing to 2.59 and 1.96% in the presence of 2 mEq/l of sodium palmitate and linoleic acid, respectively.