Generation of inorganic pyrophosphate from extracellular adenosine triphosphate by human serum and plasma.

OBJECTIVE

To quantify inorganic pyrophosphate (PPi) production from extracellular adenosine triphosphate (ATP) by human serum or plasma.

METHODS

Serial measurements of ATP hydrolysis (t1/2) were performed by the luciferase method from a starting concentration of 1 microM in serum or platelet-poor plasma incubated under physiologic conditions. ATP was then pumped into another sample of each specimen using the rate constant derived from the ATP t1/2 of that specimen. Trace (32P) gamma ATP was added at the start of the infusion; conversion to (32P) inorganic orthophosphate (Pi) and to (32P) PPi was determined by precipitation of Pi as reduced phosphomolybdate before and after treatment with yeast pyrophosphatase.

RESULTS

ATP was hydrolyzed by all serum and plasma specimens; the rate of hydrolysis in serum and plasma from the same blood sample was nearly identical. PPi was the major product, averaging 71%.

CONCLUSION

PPi is the major product of ATP catabolism in serum and platelet-poor plasma.