Microdetermination of plasma ATP and creatine phosphate concentrations with a luminescence biometer

We optimized conditions for determination of adenosine-5'-triphosphate (ATP) and creatine phosphate from plasma extracted with ethanol/water (96/4 by vol). The procedures utilize the firefly luciferin/luciferase reaction, the bioluminescence being measured with a Du Pont Biometer. ATP is quantitated directly and creatine phosphate is quantitated by reaction with creatine kinase and ADP, after plasma ATP is removed by incubation with the enzyme apyrase. The method is applied to plasma from humans, rabbits, and rats, and possible clinical applications are discussed.