Effect of captopril and enalapril on zinc metabolism in hypertensive patients

It has been shown that chronic administration of captopril (Cap), an angiotensin converting enzyme inhibitor (ACEI), is associated with renal zinc (Zn) loss which brings about a decrease in RBC Zn content. We investigated, prospectively, the effect of Cap and enalapril (En) on Zn metabolism in hypertensive patients (Pts). Two groups of Pts with newly diagnosed E.H.:18 hypertensives on En treatment alone for 6 mo; 16 hypertensives treated with Cap for 6 mo. and 10 healthy persons. Plasma, mononuclear and urine were assessed for Zn concentration before drug initiation and 6 mo. thereafter, by atomic absorption spectrophotometer. No change in plasma Zn levels was seen. Mononuclear Zn content (nmol/mg protein) decreased from 5.8±2.4 to 3.9±1.2 (p<0.01) and from 5.3±2.5 to 4.1±2.3 (p<0.04) in the Cap and EN groups, respectively. 24 h urinary Zn levels (ng/24h) in the Cap group were significantly enhanced at the end from 461±32 to 1244±15.4 (p<0.001). In the En group the increase was from 508±55 to 610±7.3 (not significant). Chronic administration of ACEI results in chronic Zn depletion as is reflected by intracellular zinc. Serum Zn does not reflect Zn depletion. It is important to be aware of clinical symptoms in Zn deficiency (skin changes, loss of appetite, mental lethargy) in chronic hypertensive Pts treated with Cap or En.