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(Hypertension. 1998;31:1201-1202.)
© 1998 American Heart Association, Inc.

Letters to the Editor

Is Plasma Ac-SDKP Level a Reliable Marker of Chronic Angiotensin-Converting Enzyme Inhibition in Hypertensive Patients?

Yannick Le Meur; ; Jean-Claude Aldigier

Service de Néphrologie, Centre Hospitalier Universitaire, Limoges, France

Vincent Praloran

Laboratoire d'Hématologie Expérimentale, Faculté de Médecine, Limoges, France

To the Editor:

In a recent article, Azizi et al¹ suggested that the plasma levels of N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) could be a reliable marker of chronic angiotensin-converting enzyme (ACE) inhibition in hypertensive patients treated by ACE inhibitors (ACEI). We were concerned by their results because some of them contradict while others agree with several of our very recent findings. The tetrapeptide Ac-SDKP (molecular weight, 487 D), a physiological inhibitor of the proliferation of hematopoietic stem cells² that is present in normal plasma at stable concentrations,³ is degraded by ACE both in vitro and in vivo.^{4 5} In a previous study in healthy volunteers, Azizi et al⁶ showed that a single oral dose of captopril, an ACEI, transiently increases the plasma levels of Ac-SDKP. In a recent study, we showed that 15-day treatment of healthy volunteers by another ACEI (enalapril) permanently increases the plasma concentrations and daily urinary elimination of Ac-SDKP by approximately 4-fold and modifies the levels of blood hematopoietic progenitors.⁷ In the Hypertension article cited above, Azizi et al¹ showed that chronic treatment of hypertensive patients by any type of ACEI permanently increased plasma Ac-SDKP levels by 5 times compared with levels in non-ACEI hypertensive patients or healthy control subjects. They thus suggested that plasma Ac-SDKP levels could be a better marker of the compliance of hypertensive patients to their chronic ACEI treatment than the currently used markers of ACE activity, such as plasma renin or angiotensin II/angiotensin I ratio. Azizi et al also found evidence that the plasma Ac-SDKP levels . . . [Full Text of this Article]

Michel Azizi

Broussais Hospital Clinical Investigation Center, INSERM and Assistance Publique des Hôpitaux de Paris, Paris, France

Eric Ezan

Service de Pharmacologie et d'Immunologie CEA, Gif-sur-Yvette, France