Effects of the angiotensin-converting enzyme inhibitor enalapril on blood haematopoietic progenitors and acetyl-N-Ser-Asp-Lys-Pro concentrations.

Acetyl-N-Ser-Asp-Lys-Pro (AcSDKP) is a physiological inhibitor of the proliferation of haematopoietic stem cells. In 12 healthy volunteers treated with the angiotensin-converting enzyme (ACE) inhibitor enalapril (20 mg day-1 for 15 days), we studied plasma and urinary AcSDKP levels, the in vitro degradation of AcSDKP by plasma ACE and the numbers of circulating haematopoietic progenitors (granulocyte-monocytic colony forming unit: CFU-GM; burst forming unit-erythroid: BFU-E; and mixed colony forming unit: CFU-mixed). During treatment, plasma and urinary AcSDKP concentrations increased 2- to 5-fold, degradation of AcSDKP was reduced, and CFU-mixed significantly increased by 100% while BFU-E and CFU-GM significantly decreased by 16% and 26%, respectively. These results indicate that ACE inhibitors may be of value during chemotherapy or radiotherapy, warranting further study.