Radioimmunoassay for adenosine in biological samples

A sensitive and specific radioimmunoassay for adenosine has been developed. Antibodies directed against adenosine (titer 1:400--1:700) were obtained by immunizing rabbits with adenosine, conjugated via its vicinal hydroxyl groups to bovine serum albumin (periodate oxidation). Interfering adenosine deaminase activity was removed from the antisera by treatment with DEAE-cellulose. Free and antibody bound 3H-adenosine was separated by either the "second antibody" precipitation method or by a simple filtration step. The sensitivity and assay range for adenosine was 1--100 pmoles per assay tube. Structurally related purine compounds (adenine nucleotides, adenine) crossreacted with adenosine binding and were removed by a single chromatographic step. Analysis of the adenosine content in normoxic guinea pig hearts yielded 2.53 nmoles/g, a value which was confirmed by spectrophotometric analysis.