Cyclic AMP concentrations in human peripheral blood lymphocytes. Changes in association with cell purification

In studies over a several year period of cAMP in human peripheral blood lymphocytes, a wide range of concentrations has been noted from low values (1 to 5 pmole/10⁷ cells) to high values (80 to 160). Evaluation of this variation indicated that between cell separation and completion of the experiment, there was a progressive decrease in lymphocyte cAMP as determined by RIA or immunocytochemistry. After a 2 hr incubation at 37 °C, a new steady state was reached at 5% to 30% of the initial concentration. This phenomenon was unique to lymphocytes and not preventable by manipulation of the incubation conditions. The cause of the cAMP reduction was shown to be decreasing AC activity. These data suggested the possibility that AC was activated during cell isolation. However, the phenomenon was present in cells not exposed to dextran or Ficoll-Hypaque, and simulation of conditions employed during purification did not result in increased cAMP. Consequently, high-lymphocyte cAMP concentrations may be the normal levels in vivo.