The binding of salicylate to plasma protein from several animal species

Abstract

A comparison has been made of the binding of salicylate to plasma from man, green monkey, rabbit, rat, dog, and guinea-pig. Since the total protein content of normal, citrated, pooled plasmas of these species was not identical, comparisons were made with samples adjusted to the same total protein concentration. The % binding to plasmas of 5·3% total protein at 50 μg of drug/ml was found to be: man, 72%; green monkey, 70%; guinea pig, 64%; rabbit, 64%; rat, 47%; dog, 45%. Results for 150 μg and 500 μg of salicylate/ml are also reported. The albumin: globulin ratio as determined by electrophoresis varied widely among the species. Fractionation of the plasmas and comparison of binding, using 3% solutions of the various albumin fractions in buffer, indicated that the low binding of dog and rat plasmas was due primarily to the low binding affinity of the albumins. Adequate characterization of plasma samples is needed when comparative binding studies are made.