We developed a simple and sensitive radioimmunoassay (RIA) for adenosine. The RIA is based on the double antibody method with adenosine 2',3'-O-disuccinyl-3-[125I]-iodotyrosine methyl ester (diSc-adenosine-[123I]-TME) as a tracer. Anti-adenosine antiserum for the RIA was raised in rabbits immunized with diSc-adenosine conjugated to human serum albumin (diSc-adenosine-HSA). All samples and standards were succinylated prior to assay. The present immunoassay allows detection of 6.25-400 pmol/ml of adenosine in sample. Values obtained by the RIA and by a HPLC analysis showed a high correlation with correlation coefficient of 0.997. In order to determine adenosine in plasmas, blood cells must be separated in the presence of 6 mM EDTA, 0.006% dipyridamole (Dip) and 23 μM 2’-deoxycoformycin (dCF) at 2°C. Adenosine in plasma could be accurately determined by the proposed method even without any pretreatments by deproteinizing. The adenosine levels with or without EDTA-treated normal human plasmas determined were 26.2 ± 7.26 and 100 ± 3.62 pmol/ml (Mean ± SEM), respectively. (KEY WORDS: adenosine, radioimmunoassay (RIA), dipyridamole, plasma adenosine level, EDTA, deoxycoformycin).
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