The inhibitors of angiotensin converting enzyme (ACE), captopril and enalapril, were found to increase ACE concentration in cultured human endothelial cells from cord artery as measured with a novel ACE assay employing MK 351A, an inhibitor of ACE, and with immunofluorescense labeling using anti-human lung ACE antibody. Dexamethasone (10 nM) also increased ACE and potentiated the increase of cellular ACE caused by captopril. Similar effects of ACE inhibitors were seen in cultured human macrophages, particularly after prestimulation with E. coli lipopolysaccharide. In Wistar Kyoto rats, captopril caused a 3-fold increase of serum ACE, while dexamethasone (40 ug/day, 14 days) did not increase serum ACE. Combined treatment with captopril and dexamethasone caused a 5-fold increase of ACE in purified lung plasma membranes. ACE inhibitors induce increased ACE biosynthesis in endothelial cells, and in macrophages. The rise of cellular ACE with ACE inhibitors is potentiated by glucocorticoid.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1983

Regulation of angiotensin converting enzyme.

Angiotensin converting enzyme (ACE;EC 3.4.15.1), or kininase II, was studied in serum, cultured endothelial cells from cord artery, in macrophages of humans, and in serum and purified plasma membranes of rats following treatment with inducers of ACE biosynthesis. ACE activity was measured in biological fluids with an enzyme kinetic method employing synthetic 1-hipp-1-his-l-leu tripeptide as a substrate, and with a new method using 125I-labelled specific inhibitor of ACE as a sensitive probe for ACE binding sites. The latter technique also proved suitable for the quantification of ACE in cells. Anti-human ACE antibody was employed for immunofluorescence studies in human cells. Dexamethasone treatment caused an increase in ACE in cultured human endothelial cells, macrophages and in rat pulmonary plasma membranes, but failed to increase serum ACE activity in rats. Captopril and enalapril treatment of hypertensive patients increased total serum ACE, the increase being evident after removal of the active drug from the serum by prolonged storage or chloramine T treatment (captopril) or by dialysis (enalapril). Captopril increased the ACE content of endothelial cells and macrophages. Macrophages appeared sensitive to captopril induction of ACE biosynthesis after pre-stimulation with Escherichia coli lipopolysaccharide. Dexamethasone treatment potentiated the known induction of ACE in rat pulmonary tissue. Thus ACE biosynthesis may be enhanced by three categories of treatment: (1) glucocorticoid; (2) macrophage activation; (3) ACE inhibitors. The precise mechanism of ACE induction and its possible biological relevance await further clarification.

Adult↗

PubMed1982

Induction of angiotensin-converting enzyme with the ACE inhibitory compound MK-421 in rat lung.

Having observed that treatment of rats with captopril led to an increased ACE activity in serum and ACE concentration in lungs, we treated female Wistar Kyoto rats for 7 days with the esterified ACE inhibitor, MK-421 (1.0 mg/kg body weight per day), administered by Alzet osmotic minipump. Serum ACE activity decreased by 67% during MK-421 treatment when measured in non-dialyzed serum samples. Removal of the drug by dialysis unmasked a 280% increase of serum ACE activity. ACE concentration of crude lung homogenate increased 134% in MK-421-treated rats and ACE concentration in purified pulmonary plasma membranes increased by 34%. The increase of serum and lung ACE in MK-421-treated rats was similar to that seen in rats treated with captopril, and was probably due to induction of ACE biosynthesis. The mechanisms of this induction are unknown.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1982

Induction of angiotensin I-converting enzyme in rat lung with captopril: the effect of adrenalectomy.

In spontaneously hypertensive rats, treatment with captopril, 0.2 g/liter of drinking fluid for 12 to 24 weeks, caused a threefold increase in serum angiotensin I-converting enzyme activity. Angiotensin I-converting enzyme increased 25 to 120 percent in lung plasma membranes. The elution profile of angiotensin I-converting enzyme on DEAE cellulose and after gel filtration on Sepharose 4B was unchanged by captopril. The Km value value also remained unchanged. In Wistar rats subjected to bilateral adrenalectomy, treatment with the same dose of captopril for 3 days resulted in increased serum angiotensin I-converting enzyme activity in both sham-operated and adrenalectomized rats, but angiotensin I-converting enzyme concentration increased in lung plasma membranes from sham-operated rats and captopril-treated rats only. We conclude that captopril causes induction of angiotensin-converting enzyme biosynthesis in spontaneously hypertensive and Wistar rats. The change is a quantitative one. Intact adrenal glands may be important for the incorporation of angiotensin I-converting enzyme into lung membranes.

Adrenal Glands↗

PubMed1982

Induction of angiotensin I-converting enzyme by captopril in cultured human endothelial cells.

Captopril (2.0 microgram/ml) increased angiotensin-converting enzyme (ACE, kininase II) activity from 6- to 16-fold in culture medium of human endothelial cells from umbilical cord artery. Immunohistochemically detectable ACE was markedly increased in these cells when using rabbit antihuman lung ACE antiserum. This accords with either observations of increased ACE activity in serum and lungs from rats treated with captopril and shows induction of ACE biosynthesis in human vascular endothelial cells in culture. This observation offers a tool for studying the mechanism of ACE induction.

Captopril↗

PubMed1981

Blood monocytes and serum and bone marrow lysozyme in sarcoidosis.

Serum lysozyme (LZM) concentrations were correlated to the number of neutrophils and monocytes in patients with sarcoidosis and nongranulomatous diseases. In sarcoidosis patients with an increased activity of serum angiotensin converting enzyme (ACE), a positive correlation was noted between LZM and blood monocytes. In sarcoidosis patients with normal ACE activity, as well as in patients with non-granulomatous diseases, a correlation was found between blood neutrophils and LZM, but not between blood monocytes and LZM. LZM was found in bone marrow plasma and in serum in a ratio of 1.5 to 1. Sarcoidosis patients had 30% higher LZM levels than healthy controls. The concentration of LZM in bone marrow plasma did not correlate to detectable granulomas in bone marrow specimens. The positive correlation between blood monocytes and LZM in patients with clinically active sarcoidosis is possibly due to recruitment of bone marrow monocytes for the granuloma formation.

Bone Marrow↗

PubMed1981

Dissociation of the effect of captopril on blood pressure and angiotensin converting enzyme in serum and lungs of spontaneously hypertensive rats.

Spontaneously hypertensive rats (SHR) of the Okamoto-Aoki strain (n = 40) were treated with captopril (SQ 14,225; D-3-mercapto-2-methylpropanoyl-L-proline) orally, dose 0.2 mg/ml in drinking water. The treatment was initiated early and later during the course of developing hypertension. Continuously treated rats did not develop hypertension. Rats receiving captopril for 12 weeks remained normotensive, whereas withdrawal of the drug resulted in hypertension. Captopril treatment was effective in the rats with established hypertension and decreased the blood pressures to nearly normal values. Serum angiotensin converting enzyme (ACE) activity rose 3-fold in captopril treated rats. ACE in lung plasma membranes increased during captopril treatment, indicating that captopril induced biosynthesis of pulmonary ACE. No qualitative differences were found in the ACE from treated and not treated animals. The dissociation of the antihypertensive effect of captopril and of increased ACE activity in serum and lungs reduce the value of relating blood pressure effects of the drug to measured enzyme activity in the SHR.

Animals↗

PubMed1980

Induction of angiotensin I-converting enzyme rat lung with Captopril (SQ 14225).

Angiotensin I-converting enzyme (ACE, EC 2.4.15.1.) was measured in serum and in pulmonary plasma membranes of 40 spontaneously hypertensive rats (SHR, Okamoto Aoki strain), divided into 4 groups, and treated with SQ 14225 (Captopril), 0.2 mg . ml-1 in drinking water, for 0-24 weeks. Serum ACE activity increased 2.5-3 fold after 12-24 weeks of SQ 14225 treatment, paralleled by an increase of ACE concentration in purified pulmonary plasma membranes (25-52%), and in ACE concentration upon solubilization with Triton X-100 from such plasma membranes (96-120%). We conclude that the ACE inhibitor, SQ 14225, causes marked induction of pulmonary ACE biosynthesis. High serum ACE activity probably reflects increased total biosynthesis of the enzyme.

Animals↗

PubMed1980

Purification of human lung angiotensin-converting enzyme.

Angiotensin-converting enzyme (ACE) was purified about 7000 times from human lung tissue obtained at thoracotomy. After solubilization with Triton X-100 and sonication, ion exchange DEAE cellulose chromatography and Sepharose 4B gel filtration were performed. After gel filtration a 5-6 fold increase in purity was achieved by neuraminidase treatment of the protein and recycling over DEAE cellulose. Purity was established in SDS electrophoresis and on electrofocusing 125I-labelled purified protein and these procedures indicated a molecular weight of about 150,000 and pI value of 4.5, respectively. The purified protein split Angiotensin I and this action was inhibited by Captopril (Squibb 14,225), specific inhibitor of ACE (kininase II). The Km value for the synthetic substrate hippuryl-histidyl-leucine was 3.7 X 10(-4) mol/l. The IC50 of Captopril when inhibiting human lung ACE action on the same substrate, was 4.5 X 10(-9) mol/l.

Chromatography, Gel↗

PubMed1980

Angiotensin converting enzyme. V. Serum levels as monitors of disease activity in corticosteroid-treated sarcoidosis.

Serum angiotensin-converting enzyme (ACE) activity was related to clinical markers of disease activity, mainly chest X-rays, pulmonary function tests and serum lysozyme (LZM) in 41 sarcoidosis patients, who received corticosteroid treatment. Increased ACE activity before treatment predicted improvement of diffusion capacity during treatment, whereas chest X-rays improved regardless of the initial ACE value. ACE decreased after initiation of treatment both in sarcoidosis patients and in healthy volunteers. In sarcoidosis most decreases were parallelled by similar LZM changes, which did not occur in volunteers. When an apparently stable state had been achieved, ACE was no longer a reliable monitor of disease activity. It often fluctuated within normal limits without accompanying clinical or LZM changes. It was not dose-dependent during daily medication but increased during alternate day administration. This may reflect decreased suppression of ACE by steroids but may also indicate reactivation of the disease process. Elevated ACE values after cessation of treatment preceded or parallelled a relapse. LZM values did not add to the information provided by ACE measurements before, during or after treatment.

Adrenal Cortex Hormones↗

PubMed1979

Angiotensin-converting enzyme. I. Activity and correlation with serum lysozyme in sarcoidosis, other chest or lymph node diseases and healthy persons.

Serum angiotensin-converting enzyme (ACE) activity was studied in healthy controls, in 57 untreated sarcoidosis patients, and in 164 patients with other chest or lymph node diseases. The serum ACE activity of healthy persons was independent of sex, intake of meals, and smoking habits. There were no diurnal variations. Healthy children had a significantly higher ACE mean value than adults, whose ACE activity was not affected by age. The sarcoidosis patients had the highest ACE mean values, but those of patients with silicosis and asbestosis were also significantly elevated. Pulmonary cancer patients had decreased serum ACE activity, which was probably due to antimitotic treatment. Serum lysozyme (LZM) concentrations did not correlate with normal ACE activity, but the correlation between elevated ACE and LZM was significant in sarcoidosis and silicosis, and the trend was clearly the same for asbestosis. This indicates separate sources for these enzymes when ACE activity is normal, and a common source, i.e. macrophages, when ACE activity is increased. ACE production in certain diseases involving macrophages may be due to the bradykinin inhibiting effect of this enzyme.

Adolescent↗

PubMed1979

Angiotensin-converting enzyme. II. Serum activity in early and newly diagnosed sarcoidosis.

Serum angiotensin-converting enzyme (ACE) was studied in 51 patients with early or newly diagnosed sarcoidosis. Only 45% of these patients had increased ACE activity when their diagnosis was established, which diminishes the diagnostic value of this enzyme measurement. On the other hand, ACE accurately reflected disease activity, and it proved a useful tool for assessing of need for corticosteroid treatment. Patients with acute sarcoidosis associated with erythema nodosum (EN) had low ACE activity compared with the other patients with active, but less acute disease. Serum ACE was not significantly correlated with blood lymphocytes or the immunoglobulins, but there was a positive correlation between the enzyme and serum lysozyme, which strengthens the hypothesis of both enzymes being produced by the epithelioid cells of sarcoid granulomas.

Adult↗

PubMed1979

Angiotensin converting enzyme. III. Changes in serum level as an indicator of disease activity in untreated sarcoidosis.

The activity of serum angiotensin converting enzyme (ACE) was repeatedly measured together with serum lysozyme (LZM) in patients with untreated sarcoidosis. Changes in the clinical picture were registered using chest X-ray, forced vital capacity (FVC), diffusing capacity for carbon monoxide (DLCO) and appearance of extrapulmonary lesions. During a clinically unchanged period the highest ACE activity and the corresponding LZM value (not the highest value) were used for the calculation. A statistically significant change in ACE was noted when a normal chest X-ray changed to a stage II lesion or vice versa, and when a signficant change in FVC occurred. All other changes were insignificant. On the other hand, statistically significant changes in ACE were found during stable periods according to chest X-ray, FVC or DLCO. ACE is frequently elevated in serum of patients with active sarcoidosis. The fluctuations in activity mostly parallel the clinical course of the disease. The behaviour and metabolism of the enzyme need further investigation. An increased concentration of serum LZM is frequent in patients with active sarcoidosis. The highest LZM values are not always seen simultaneously with the highest ACE values, indicating that they probably express different dimensions of the disturbances in the sarcoid granuloma.

Adult↗