Activity of cyclic nucleotide phosphodiesterases in granulocytes of chronic myelogenous leukemia (CML). A preliminary report.

Cyclic 3':5'-adenosinmonophosphate phosphodiesterase (cAMP-PDE), high KM value type isoenzyme, and cyclic 3':5'-guanosino-monophosphate phosphodiesterase (cGMP-PDE), high KM value type isoenzyme, were determined in granulocytes of patients with chronic myelogenous leukemia (CML) in the chronic phase of the disease. Granulocyte cAMP-PDE activity was similar in the general group of CML patients to that in normal granulocytes; the cGMP-PDE, however, was somewhat higher. By dividing the CML general group into the "low leukocyte count" subgroup including granulocytes of patients with WBC number ranging from 10,300 to 40,000 per microliter (mean 22,000 per microliter), and the "high leukocyte count" subgroup including patients with leukocyte count above 40,000 per microliter (mean 67,000) remarkable differences in the activities of cyclic nucleotide phosphodiesterases between these subgroups could be found: cAMP-PDE activity for the high leukocyte count subgroups was significantly higher than for that in normals, and in CML-low leukocyte count subgroup. On the other hand, cGMP-PDE activity in granulocytes of the high leukocyte count subgroup was found to be remarkably lower than that in normals, in the low leukocyte count subgroup and general CML group. In CML patients the ratio of cAMP-PDE activity to cGMP-PDE activity was always considerably higher than that in controls. The obtained results suggest CML granulocytes to differ from normal ones in respect to their control of intracellular cyclic nucleotide levels. This difference is related to the accumulation of CML granulocytes.