Determination of an endothelin receptor antagonist in rat plasma by radioimmunoassay.

A quantitative method based on radioimmunoassay for the determination of an endothelin receptor antagonist (C(31)H(33)NO(7), I) has been developed and validated. The immunogen was prepared by coupling I to the bovine serum albumin via the N-hydroxysuccinimide ester of I from which the radioligand was also prepared by the reaction with [125I]-iodotyrosine. The method was specific and no immunoactive material other than the parent drug was detectable in mammalian plasma. This direct assay, using 50 microl of rat plasma is sensitive (0.4 ng/ml), without matrix interference, and has sufficient sensitivity, specificity, accuracy and precision for the analysis of dosed rat plasma samples.

Development and implementation of an electrochemiluminescence immunoassay for the determination of an angiogenic polypeptide in dog and rat plasma.

A quantitative method based on electrochemiluminescence immunoassay for the determination of the angiogenic agent aFGF-S117 has been developed and validated. Two polyclonal antibodies specific to aFGF-S117 and a wild-type aFGF antibody were selected for the analysis. The assay was based on the non-competitive sandwich immunoassay principle in which the drug is trapped with a biotinylated antibody that is immobilized on a streptavidin magnetic particle. The drug is then sandwiched with a ruthenium chelated second antibody. The assay demonstrates good accuracy and reproducibility at plasma concentration of 0.5 ng/ml.