Bioactive carbohydrates—In chemistry,biochemistry, and biology: By J. F. Kennedy and C. A. White,Halsted Press,New York, 1983, 331 pp. $79.95

A method for analysis of plasma adenosine which combines the principles of radioisotope dilution and enzymatic catalysis is presented. Plasma from venous heparinized blood containing the adenosine deaminase inhibitor 2′-deoxycoformycin is mixed with a small amount of [³H]adenosine and extracted with perchloric acid. Using highly purified enzyme and [γ-³²P]GTP as the phosphate donor, the neutralized extract then serves as substrate for adenosine kinase, and the AMP product is purified by high-performance liquid chromatography. Adenosine concentrations in plasma are linearly proportional to ${}^{32}\text{P}{}^3\text{H}$ ratios in the enzymatically synthesized AMP and are calculated from a standard curve. The advantages of the method are: ease of sample preparation; sensitivity of 20 nm in as little as 0.3 ml plasma; 20 samples per day can be analyzed by a single operator. Care must be used when obtaining plasma since cellular contamination will affect results. Using this assay, human plasma adenosine levels are 0.121 ± 0.054 μm for males and 0.101 ± 0.067 μm for females.