Measurement of Femtomolar Concentrations of Adenosine

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Abstract
A method is described for the measurement of femtomole quantities of adenosine. Standards of adenosine or samples of biological fluids or tissues (after deproteinization) are subjected to standard, gradient, reversed phase HPLC. The adenosine fraction is collected, enzymatically converted to uric acid and the uric acid quantified by electrochemical detection. Peak height in millimeters or nanoamperes is linearly related to adenosine levels over a range of 25–2000 fmoles. As little as 5 fmoles of adenosine can be detected and 25 fmoles can be accurately measured. The adenosine concentration of Krebs-Henseleit solution in contact with the epicardial surface of the dog heart reaches apparent equilibrium with the interstitial fluid concentration of the myocardium within 2–4 min at a level of 0.15 μM (range 0.08–0.24 μM).