The assessment of serum ACE activity in COVID-19 and its association with clinical features and severity of the disease.

Angiotensin-converting enzyme (ACE)/Angiotensin (Ang) II pathway has crucial regulatory effects on circulatory hemostasis and immune responses. This pathway has a major role in the development of acute lung injury and acute respiratory distress syndrome (ARDS), which is a devastating complication of SARS-CoV-2 infection. The aim of this study is to investigate the serum ACE activity and its correlation with clinical features and the disease severity in patients with COVID-19. Patients with confirmed COVID-19 by detecting SARS-CoV-2 nucleic acid RT-PCR were included in the study. Demographic data, clinical features, laboratory and radiologic investigations were recorded. Patients were classified by disease severity; asymptomatic, mild, and severe pneumonia. The serum ACE activity was evaluated with an autoanalyzer based on a spectrophotometric method. Fifty-five patients (50.9% female) and 18 healthy subjects (33.3 % female) were enrolled in the study. The median age of patients was 40 years, ranging from 22 to 81 years. Eighteen healthy subjects were served as the control group. The baseline characteristics were comparable between groups. The median serum ACE activity of patients and controls (38.00 [IQR 21] U/L and 32.00 [IQR 24] U/L, respectively) and of between patients grouped by disease severity (38.5 [IQR 19], 36 [IQR 25], and 38 [IQR 22] U/L, asymptomatic, mild and severe pneumonia group, respectively) were similar. There was no correlation between the serum ACE activity and conventional inflammatory markers. In this study, we did not find an association between serum ACE activity and COVID-19 and serum ACE activity on admission did not reflect disease severity.

Assessment of Hypokalemia and Clinical Characteristics in Patients With Coronavirus Disease 2019 in Wenzhou, China.

Importance: Severe acute respiratory syndrome coronavirus 2 has caused a global outbreak of coronavirus disease 2019 (COVID-19). Severe acute respiratory syndrome coronavirus 2 binds angiotensin-converting enzyme 2 of the rennin-angiotensin system, resulting in hypokalemia. Objective: To investigate the prevalence, causes, and clinical implications of hypokalemia, including its possible association with treatment outcomes, among patients with COVID-19. Design, Setting, and Participants: This cohort study was conducted at Wenzhou Central Hospital and Sixth People's Hospital of Wenzhou, Wenzhou, China, from January 11, 2020, to February 15, 2020. Participants included patients who received a diagnosis of COVID-19 according to the criteria issued by the Chinese Health Bureau and were admitted to the hospital. The patients were classified as having severe hypokalemia (plasma potassium <3 mmol/L), hypokalemia (plasma potassium 3-3.5 mmol/L), and normokalemia (plasma potassium >3.5 mmol/L). The clinical features, therapy, and outcomes were compared between the 3 groups. Data analysis was conducted in March 2020. Interventions: The patients were given general support and antiviral therapy. Their epidemiological and clinical features were collected. Main Outcomes and Measures: The prevalence of hypokalemia and response to treatment with potassium supplements were measured by analyzing plasma and urine potassium levels. Results: One hundred seventy-five patients (87 female patients [50%]; mean [SD] age, 45 [14] years) were classified as having severe hypokalemia (31 patients [18%]), hypokalemia (64 patients [37%]), and normokalemia (80 patients [46%]). Patients with severe hypokalemia had statistically significantly higher body temperature (mean [SD], 37.6 °C [0.9 °C]) than the patients with hypokalemia (mean [SD], 37.2 °C [0.7 °C]; difference, 0.4 °C; 95% CI, 0.2-0.6 °C; P = .02) and the patients with normokalemia (mean [SD], 37.1 °C [0.8 °C]; difference, 0.5 °C; 95% CI, 0.3-0.7 °C; P = .005). Patients with higher levels of hypokalemia also had higher creatine kinase levels (severe hypokalemia, mean [SD], 200 [257] U/L [median, 113 U/L; interquartile range {IQR}, 61-242 U/L]; hypokalemia, mean [SD], 97 [85] U/L; and normokalemia, mean [SD], 82 [57] U/L), higher creatine kinase-MB fraction (severe hypokalemia, mean [SD], 32 [39] U/L [median, 14 U/L; IQR, 11-36 U/L]; hypokalemia, mean [SD], 18 [15] U/L; and normokalemia, mean [SD], 15 [8] U/L), higher lactate dehydrogenase levels (mean [SD], severe hypokalemia, 256 [88] U/L; hypokalemia, 212 [59] U/L; and normokalemia, 199 [61] U/L), and higher C-reactive protein levels (severe hypokalemia, mean [SD], 29 [23] mg/L; hypokalemia, mean [SD], 18 [20] mg/L [median, 12, mg/L; IQR, 4-25 mg/L]; and normokalemia, mean [SD], 15 [18] mg/L [median, 6 U/L; IQR, 3-17 U/L]). Of 40 severely and critically ill patients, 34 (85%) had hypokalemia. Patients with severe hypokalemia were given potassium at a dose of 40 mEq per day, for a total mean (SD) of 453 (53) mEq potassium chloride, during the hospital stay. The patients responded well to potassium supplements as they recovered. Conclusions and Relevance: The correction of hypokalemia is challenging because of continuous renal potassium loss resulting from the degradation of angiotensin-converting enzyme 2. The high prevalence of hypokalemia among patients with COVID-19 suggests the presence of disordered rennin-angiotensin system activity, which increases as a result of reduced counteractivity of angiotensin-converting enzyme 2, which is bound by severe acute respiratory syndrome coronavirus 2.

Assessment of the rs4340 ACE gene polymorphism in acute coronary syndrome in a Western Mexican population.

Acute coronary syndrome (ACS) is considered one of the main causes of death worldwide. Contradictory findings concerning the impact of the angiotensin-converting enzyme (ACE) gene on cardiovascular diseases have been reported. Previous conclusions point out that the variability in results depends on ethnicity and genetic polymorphisms to determine the association of rs4340 polymorphisms of the ACE gene and ACE circulating levels in ACS. Genotyping of rs4340 polymorphisms was performed in a total of 600 individuals from Western Mexico divided into two groups: the ACS and the control group (CG). The polymorphisms were identified by polymerase chain reaction. Serum ACE concentration was determined by enzyme-linked immunosorbent assay. D/D carriers had higher ACE levels than I/I carriers (3.6 vs 2.8 ng/mL, P < 0.0021) in the CG. The D/D genotype of the rs4340 polymorphism is associated with higher ACE concentration levels; however, the polymorphism was not associated with ACS.

Bayesian network ensemble as a multivariate strategy to predict radiation pneumonitis risk.

PURPOSE: Prediction of radiation pneumonitis (RP) has been shown to be challenging due to the involvement of a variety of factors including dose-volume metrics and radiosensitivity biomarkers. Some of these factors are highly correlated and might affect prediction results when combined. Bayesian network (BN) provides a probabilistic framework to represent variable dependencies in a directed acyclic graph. The aim of this study is to integrate the BN framework and a systems' biology approach to detect possible interactions among RP risk factors and exploit these relationships to enhance both the understanding and prediction of RP. METHODS: The authors studied 54 nonsmall-cell lung cancer patients who received curative 3D-conformal radiotherapy. Nineteen RP events were observed (common toxicity criteria for adverse events grade 2 or higher). Serum concentration of the following four candidate biomarkers were measured at baseline and midtreatment: alpha-2-macroglobulin, angiotensin converting enzyme (ACE), transforming growth factor, interleukin-6. Dose-volumetric and clinical parameters were also included as covariates. Feature selection was performed using a Markov blanket approach based on the Koller-Sahami filter. The Markov chain Monte Carlo technique estimated the posterior distribution of BN graphs built from the observed data of the selected variables and causality constraints. RP probability was estimated using a limited number of high posterior graphs (ensemble) and was averaged for the final RP estimate using Bayes' rule. A resampling method based on bootstrapping was applied to model training and validation in order to control under- and overfit pitfalls. RESULTS: RP prediction power of the BN ensemble approach reached its optimum at a size of 200. The optimized performance of the BN model recorded an area under the receiver operating characteristic curve (AUC) of 0.83, which was significantly higher than multivariate logistic regression (0.77), mean heart dose (0.69), and a pre-to-midtreatment change in ACE (0.66). When RP prediction was made only with pretreatment information, the AUC ranged from 0.76 to 0.81 depending on the ensemble size. Bootstrap validation of graph features in the ensemble quantified confidence of association between variables in the graphs where ten interactions were statistically significant. CONCLUSIONS: The presented BN methodology provides the flexibility to model hierarchical interactions between RP covariates, which is applied to probabilistic inference on RP. The authors' preliminary results demonstrate that such framework combined with an ensemble method can possibly improve prediction of RP under real-life clinical circumstances such as missing data or treatment plan adaptation.

Angiotensin-converting enzyme for noninvasive assessment of liver fibrosis in autoimmune hepatitis.

BACKGROUND AND AIM: There are no validated noninvasive markers of liver fibrosis in autoimmune hepatitis (AIH). An activated renin-angiotensin system (RAS) and its key element angiotensin-converting enzyme (ACE) have been implicated in the pathogenesis of hepatic fibrogenesis. We aimed to study the assumed role of activated RAS in the fibrogenic process and whether the serum concentration of ACE can predict different fibrosis stages in AIH. PATIENTS AND METHODS: Serum samples of 73 consecutive patients who were diagnosed with AIH were analysed for ACE concentration. All patients underwent a liver biopsy. RESULTS: Serum ACE levels increased significantly for each fibrosis score. The median ACE was 45 U/l in patients with fibrosis score I, 54 U/l in patients with fibrosis score II, 68 U/l in patients with fibrosis score III and 87 U/l in patients with fibrosis score IV. For significant fibrosis (≤F2), a 56 U/l cut-off value of ACE had 95.5% sensitivity and 74.5% specificity, and receiver-operating characteristic curves showed an area under the curve (AUC) of 0.89. For advanced fibrosis (≤F3), a 64 U/l cut-off level of ACE had 85.2% sensitivity and 94.8% specificity, and AUC was 0.91. For cirrhosis, a 68 U/l cut-off level of ACE had 100% sensitivity and 84.4% specificity, and AUC was 0.95. CONCLUSION: Our results suggest that activated RAS may sustain hepatic fibrogenesis in AIH. Measurement of serum ACE offers an easy, accurate and inexpensive noninvasive method that differentiates significant from nonsignificant liver fibrosis in AIH. Blockade of RAS may exert beneficial effects on fibrosis progression in AIH.

Assessment of serum angiotensin-converting enzyme in patients with epithelial ovarian cancer.

BACKGROUND AND AIMS: Clinicopathologic and molecular studies have provided new insights and understanding on the pathological events during ovarian carcinogenesis. Moreover, angiotensin II-enhanced tumor cell invasion via type 1 angiotensin II receptor in ovarian cancer cell lines was recently demonstrated. It has been suggested that renin-angiotensin system (RAS) activity increases in diseases involving the female reproductive system. In the present study, we aimed to analyze the possible relationship between the levels of circulating angiotensin-converting enzyme (ACE), an important molecule of RAS, and ovarian cancer (OC). MATERIALS AND METHODS: This study was conducted in 41 epithelial OC patients (mean age 56.1 ± 10.2 years) and 19 healthy controls (mean age 53.4 ± 13.1 years). Clinical and laboratory features are summarized. Serum ACE and Ca-125 levels were measured using commercially available laboratory kits. RESULTS: Serum ACE levels of epithelial OC patients and controls were 30.58 ± 13.37 and 14.15 ± 3.67, respectively. Serum ACE levels were significantly elevated in epithelial OC patients in comparison to healthy controls. Ca-125 levels of epithelial OC patients were also significantly elevated in epithelial OC patients. No correlation was observed between ACE levels and Ca-125 levels. In epithelial OC patients, serum ACE levels did not differ according to stages and pathologic subtypes of the patients. CONCLUSION: Our results showed that serum ACE levels were increased in OC patients. Being an important component of RAS, circulating ACE might be associated with ongoing pathobiologic events in ovarian carcinogenesis. Therefore, targeting the RAS pathway could provide a future treatment strategy for this cancer type.

Central skeletal sarcoidosis: a case report with sustained remission only on methotrexate, and a literature review on the imaging approach, treatment, and assessment of disease activity.

We report a case of multifocal involvement of the central skeleton in a patient with long-term stage I pulmonary sarcoidosis who experienced sustained clinical remission of musculoskeletal symptoms while on methotrexate (MTX) alone. Concomitant normalization of laboratory tests [inflammatory markers and angiotensin-converting enzyme (ACE) levels] was observed, and improvements were seen in follow-up magnetic resonance imaging (MRI) of the lumbar spine and bone scintigraphy. To date, there are no specific tools for the assessment of skeletal disease activity in sarcoidosis. Our case suggests that inflammatory markers and ACE levels, when initially elevated, bone scintigraphy, and-in the case of vertebral involvement-MRI could serve as such tools. A literature review on the imaging approach, treatment, and disease activity monitoring of skeletal sarcoidosis is also provided.

Inflammatory activity assessment by F18 FDG-PET/CT in persistent symptomatic sarcoidosis.

BACKGROUND: Establishing inflammatory activity in sarcoidosis patients with persistent disabling symptoms is important. Whole body F(18)-FDG PET/CT (PET) appeared to be a sensitive method to detect inflammatory activity in newly diagnosed symptomatic sarcoidosis. The aim was to assess the presence of inflammatory activity using PET in sarcoidosis patients with unexplained persistent disabling symptoms and the association between PET findings and serological inflammatory markers. METHODS: Sarcoidosis patients who underwent a PET between June 2005 and June 2010 (n = 89), were retrospectively included. All PET scans were examined and positive findings were classified as thoracic and/or extrathoracic. As serological markers of inflammatory activity angiotensin-converting enzyme (ACE), soluble interleukin-2 receptor (sIL-2R), and neopterin were considered. RESULTS: In 65/89 (73%) of the studied patients PET was positive, 52 of them (80%) had serological signs of inflammatory activity. In 14/15 patients with a Chest X-ray stage IV PET was positive. In 80% of the PET positive patients extrathoracic inflammatory activity was found. Sensitivity of combined serological inflammatory markers for the presence of inflammatory activity as detected by PET was 80%, specificity 100%, positive predictive value 100%, negative predictive value 65%. CONCLUSIONS: The majority of sarcoidosis patients with persistent disabling symptoms, even those with radiological stage IV, had PET positive findings with remarkably 80% extrathoracic lesions. In 20% PET was positive without signs of serological inflammatory activity. PET appeared to be of additional value to assess inflammatory activity in patients with persistent symptoms in the absence of signs of serological inflammatory activity and to detect extrathoracic lesions.

Angiotensin-converting enzyme (ACE) I/D corrected serum ACE activity and severity assessment of community-acquired pneumonia.

BACKGROUND: Various studies have described decreased serum angiotensin-converting enzyme (ACE) activity in patients with pneumonia. The aim of the present study was to evaluate the role of ACE in pneumonia by comparing ACE insertion/deletion (I/D) genotype corrected serum ACE activity and to establish whether the severity of the disease correlates with lower ACE activity. METHODS: This was a prospective hospital-based observational study including 134 patients with pneumonia. Serum ACE activity was determined at admission, on days 2, 3, 5 and 10 of hospital stay, and at recovery. Based on ACE genotype and reference values, corresponding Z-scores were calculated. Disease severity, quantified by the acute physiology score (APS), and clinical outcome were compared between tertile groups of the Z-scores. RESULTS: A significant decrease in serum ACE activity during an episode of pneumonia with return to control range during recovery was observed for all three genotypes (II, ID and DD). The calculated Z-scores showed a negative correlation with APS scores (p=0.050). No significant association between decreased serum ACE activity and clinical outcome was observed. CONCLUSIONS: Serum ACE activity is significantly decreased during the acute phase of pneumonia. Despite correction for ACE I/D genotype, decreased ACE activity did not show a prognostic value. Further studies are needed to examine the mechanisms behind and diagnostic value of decreased ACE activity in community-acquired pneumonia.

The clinical application and cost analysis of fine-needle aspiration biopsy in the diagnosis of mass lesions in sarcoidosis.

BACKGROUND: Sarcoidosis is a prevalent disease of unknown cause characterized by granulomatous inflammation that often creates deep and/or superficial mass lesions. Tissue samples are considered the "gold standard" in diagnosis; however, it is a medically treated disease. We analyzed the utility and relative cost-effectiveness of fine-needle aspiration biopsy (FNAB) in the clinical investigation of patients with both suspected and unsuspected sarcoidosis. METHODS: All FNAB cases with sarcoidosis either as the cytologic diagnosis or mentioned as part of the differential diagnosis were retrospectively reviewed for clinical history, follow-up, cytologic features, and surgical pathology findings. Comparative analysis of cost of FNAB and excisional biopsy were also made. RESULTS: Thirty-two FNABs in 28 patients included 17 women and 11 men. Anatomic sites included lymph node (n = 17), lung (n = 5), salivary gland (n = 8), and liver (n = 2). Sarcoidosis had already been diagnosed or was a clinical consideration prior to FNAB in 14 cases. Chest radiograph showed abnormal findings in 19 cases. Angiotensin-converting enzyme (ACE) was measured in seven patients and was elevated in four. All aspirates showed granulomatous inflammation; in 22 patients, special stains or cultures for microorganisms were negative. Simultaneous or subsequent excisional biopsies confirmed the FNAB findings in 17 patients. Institutional ratios of excisional biopsy to FNAB in the diagnosis of sarcoidosis ranged from 4 to 19:1. The cost of FNAB was only 12.5 to 50% that of tissue biopsy. CONCLUSIONS: FNAB appears to be underutilized in the diagnosis of sarcoidosis. When used in conjunction with radiologic and laboratory data, FNAB may be a reliable and cost-effective method of diagnosis, especially in patients with an established diagnosis of sarcoidosis.

Assessment of renal function in the early stages of nephrotoxicity induced by iodinated contrast media.

To determine whether there are early renal function parameters (RFP) which can be monitored to rapidly detect nephrotoxicity induced by contrast media (CM), we observed RFP in 16 patients with normal renal function before and after administration of CM. Forty-eight hours after diatrizoate meglumine administration, blood urea nitrogen (BUN) and serum creatinine (SCr) increased (p < 0.05). In all patients, acute tubular damage was revealed by early urinary RFP. Increases in levels of serum angiotensin-I-converting enzyme (ACE), beta(2)-microglobulin (beta(2)M) and urinary albumin (Alb) were associated with alterations in glomerular function. The changes in early RFP occurred earlier than those of BUN and SCr. The present study demonstrates that serum ACE, beta(2)M, urinary Alb, gamma-glutamyl-transpeptidase and N-acetyl-beta-D-glucosidase are sensitive parameters for the early assessment of subclinical nephrotoxicity induced by CM.

In vivo assessment of captopril selectivity of angiotensin I-converting enzyme inhibition: differential inhibition of acetyl-ser-asp-lys-pro and angiotensin I hydrolysis.

Angiotensin I-converting enzyme (ACE) is a zinc metallopeptidase that plays a major role in blood pressure regulation. The demonstration that the hemoregulatory peptide acetyl-Ser-Asp-Lys-Pro (AcSDKP) is a natural and specific substrate of the N-active site of ACE suggests that this enzyme may have a new physiological role such as the modulation of hematopoietic stem cells. In vitro studies have shown that ACE inhibitors displayed various potencies in inhibiting the degradation of different natural or synthetic substrates of ACE, among which captopril inhibits AcSDKP hydrolysis more potently than angiotensin I hydrolysis. To look for this selectivity in vivo, we investigated the pharmacodynamic effect of increasing doses of captopril (0.01-10 mg/kg) during the 90 min after i.v. administration to spontaneously hypertensive rats. Plasma and urinary AcSDKP levels were measured. The renin-angiotensin system was evaluated by measurements of ACE activity in plasma samples, using the synthetic substrate Hip-His-Leu, by determinations of plasma renin concentrations and measurements of arterial blood pressure. The results showed that captopril (0.01-0.3 mg/kg) selectively inhibited AcSDKP hydrolysis, with limited effects on the renin-angiotensin system. AcSDKP levels in plasma and urine rose to a plateau 4 times the basal level for doses more than 0.3 mg/kg. All of the parameters reflecting the renin-angiotensin system were significantly affected at doses of 1 and 10 mg/kg. The present study therefore confirms that captopril can be used to protect hematopoietic stem cells during antitumor chemotherapy while having only a limited effect on cardiovascular homeostasis.

The practical assessment of compliance with ACE-inhibitor therapy--a novel approach.

Poor compliance may be responsible for symptomatic decompensation or neurohormonal "escape" in patients with heart failure treated over the long term with angiotensin-converting enzyme-1 (ACEI) drugs. Serum ACE activity is a poor index of neurohormonal suppression or haemodynamic effect after ACE-inhibitor treatment. Serum ACE activity may, however, be a useful index of compliance with treatment, as serum ACE is sensitive to the presence of an ACE inhibitor in the blood. Sixteen normotensive male volunteers of known ACE genotype received 7 days of randomised, double-blind therapy on four occasions 2 weeks apart with lisinopril 20 mg (L) or matched placebo (P) to simulate (A) noncompliance (all P), (B) full compliance (all L), (C) partial compliance (L days, 1, 3, 6; P days, 2, 4, 5, 7), or (D) single dose (L day 7; P, 1-6). Supine (30 min) blood pressure (BP)/heart rate (HR), ACE, and angiotensins were measured on d7 before dose and 4-6 h after dose. Results are mean +/- 1 SD. BP showed the expected small decrease with active treatment on d7 (B or D) but not with placebo (A) or partial compliance (C). Prestudy serum ACE, despite a wide range (16-124 U/L), was reproducible within subjects [coefficient of variation (CV), 1.7%]. Serum ACE activity, before (41.9 +/- 30) and after (41 +/- 30) angiotensin (A) I or II, were unaffected by treatment (placebo A). Active treatment (B) resulted in very low serum ACE activity and d7 and a small further suppression after dosing (before, 3.9 +/- 4; after, 1.8 +/- 4). AI was elevated in this group with further elevation after dosing (before, 234 +/- 116; after, 551 +/- 250). AII was only modestly reduced from baseline and showed little further suppression after dosing (before, 7.8 +/- 4; after, 6.3 +/- 5). Partial compliance (C) showed low ACE but no reduction after treatment (before, 7 +/- 3; after, 7 +/- 4), an elevated AI but no dosing effect (before, 187 +/- 198; after, 200 +/- 151) and reduced AII but with no further dose suppression (before, 6.4 +/- 3.4; after, 7 +/- 4) induced increase in peptide (compared with B). Single-dose treatment (D) showed ACE inhibition as expected (before, 47 +/- 30; after, 2.2 +/- 3). There was a dosing-related increase of AI but to a lesser extent than seen with chronic active dosing (B) (before, 39 +/- 10; after, 240 +/- 200). In contrast to long-term dosing, there was marked ANG II suppression (before, 8.8 +/- 4; after, 2.9 +/- 3). With this long-acting ACEI in a dose relevant to congestive heart failure management, we suggest that 4-6 h after-dosing serum ACE (< 5 EU/L) and elevated ANG I (> 300 pg/ml) can be used to confirm compliance with treatment. These absolute values may be altered in patients treated concomitant with loop diuretics. In principle, however, this may be a useful tool in clinical trials or in clinical practice after further work has been done to assess the limits in patients across the doses and across the range of available drugs used.

Pulmonary sarcoidosis: role of CT in the evaluation of disease activity and functional impairment and in prognosis assessment.

PURPOSE: To investigate the role of computed tomography (CT) in determining disease activity and functional impairment and in predicting the prognosis of lung involvement in patients with sarcoidosis. MATERIALS AND METHODS: Two groups of patients underwent CT, pulmonary function tests, and bronchoalveolar lavage. Disease activity was based on serum angiotensin converting enzyme activity and/or lymphocytosis at bronchoalveolar lavage. CT findings in group 1 were correlated with indexes of disease activity and functional parameters at diagnosis. In group 2, evaluation initially and at follow-up led to investigation of correlations between initial CT findings and evolution of disease activity and functional impairment. RESULTS: CT abnormalities in group 1 were nodules, air-space consolidation, lung distortion, septal and nonseptal linear areas of high attenuation, ground-glass attenuation, and honeycombing. Profusion of septal lines was the only CT finding that correlated with disease activity. Statistically significant (P < .05) but low correlation (r < .48) was observed between the extent of abnormalities at CT and impairment of lung function, except for nodules. CONCLUSION: Profusion of lung changes reflects functional impairment but not disease activity. CT findings cannot help predict the evolution of lung changes over time.

Assessment and optimization of kinetic methods for angiotensin-converting enzyme in plasma.

In the kinetic angiotensin-converting enzyme (ACE) method, a practical and optimal buffer is 80 mmol/L borate buffer at pH 8.2 (37 degrees C). A lag phase is detected in the reaction, and a 5-min incubation of substrate and plasma is suggested before the kinetic measurement. The substrate, N-[3-(2-furyl)acryloyl]-L-phenylalanylglycylglycine (FAPGG), concentration is maximized at 1.0 mmol/L and the measurement wavelength is at 345 nm to ensure linearity of measurement. The proposed procedure uses a 1:9 plasma-to-reagent volume ratio. The linear range of the assay extends to approximately 170 U/L, representing a 25% substrate hydrolysis. The FAPGG absorptivity is determined by measuring the difference in absorbance between 1.0 mmol/L FAPGG and the product solutions. The wavelength fidelity is checked by noting the expected absorbance value of the FAPGG solution, and a 1.0-nm deviation from 345 nm alters the absorbance by 15.5%. The precision of ACE assays at approximately 60 and 100 U/L is 3.5% and 2.4% within batch and 2.9% and 2.6% between batch, respectively. The reference interval (2.5th to 97.5th percentiles) is 41-139 U/L, and there is no difference between values for men and women.

Urinary neopterin in pulmonary sarcoidosis. Relationship to clinical and biologic assessment of the disease.

Neopterin is a metabolite of guanosine-triphosphate, released in vitro by macrophages under the control of gamma-interferon and described as a marker of T cell activation in vivo. We have compared the urinary neopterin/creatinine ratio (mumol/mol) in patients with pulmonary sarcoidosis (n = 66), interstitial lung diseases other than sarcoidosis (nonsarcoid ILD, n = 35), and 45 normal control subjects. For the sarcoid population as a whole, urinary neopterin was higher (496 +/- 52 mumol/mol [mean +/- SEM]) than in control subjects (126 +/- 5 mumol/mol) (p less than 0.001). In patients with nonsarcoid ILD, urinary neopterin was frequently higher in granulomatous and/or lymphoproliferative diseases (hypersensitivity pneumonitis, tuberculosis, primitive Sjögren's syndrome, and malignant lymphomas) (781 +/- 193 mumol/mol, n = 10) but remained normal in other types of nonsarcoid ILD [( 163 +/- 14 mumol/mol, n = 25]: histiocytosis X, idiopathic pulmonary fibrosis, lung collagen-vascular diseases, diffuse neoplasms, pneumoconiosis; p less than 0.001 compared with sarcoidosis). We have also evaluated the relationship between urinary neopterin and the clinical or biologic markers currently used to assess sarcoidosis: alveolar lymphocytosis in lavage fluid (ALY), 67-gallium scan semiquantitative index (67Ga), or serum angiotensin-converting enzyme (SACE). Sarcoid patients with the highest urinary neopterin were those in whom mean values of these markers were the highest (p less than 0.05, all comparisons). Patients with positive markers (i.e., either clinical expression of sarcoidosis-ALY greater than 30%-67Ga greater than 20-SACE greater than 60 U/ml) had significantly higher urinary neopterin levels than did other sarcoid patients (p less than 0.05, all comparisons).

The assessment of ACE activity in man following angiotensin I challenges: a comparison of cilazapril, captopril and enalapril.

1. The aim of the studies was to develop a new methodology to estimate the pharmacodynamic properties and potency of angiotensin converting enzyme (ACE) inhibitors in man. 2. Angiotensin I dose-response curves were derived by continuous infusion of angiotensin I in increasing dose steps; steady state was reached within 3 min. 3. Interaction between angiotensin I (agonist) and ACE inhibitors (antagonist) was characterized according to Schild-plot methodology by measuring agonist dose-response curves using diastolic blood pressure in the absence and the presence of varying doses of the antagonist. 4. Cilazapril shifted the angiotensin I dose-response curves to the right. A twofold shift (apparent Ki-dose) was observed with approximately 0.6 mg cilazapril. 5. The effect of angiotensin I on diastolic blood pressure was determined before and up to 36 h after administration of 25 mg captopril, 10 mg enalapril, 4 mg cilazapril and a placebo orally. The pharmacodynamic half-life of captopril was about 2 h, whereas the effect of enalapril and cilazapril was about 4 h. 6. Angiotensin I dose-response curves are useful methods of investigating the pharmacodynamic properties of ACE-inhibitors in man.

Assessment of kininases in rheumatic diseases and the effect of therapeutic agents.

Bradykinin is degraded in human plasma by a carboxypeptidase to yield desArg9-bradykinin (DBK) which is then digested by angiotensin-converting enzyme (ACE) to the pentapeptide Arg-Pro-Pro-Gly-Phe and the tripeptide Ser-Pro-Phe. We have studied the rate of kinin degradation by each of these enzymes in patients with rheumatoid arthritis (RA) and with systemic lupus erythematosus (SLE), compared with the degradation rate in degenerative joint disease and normal subjects. Carboxypeptidase activity was the same in all individuals, but ACE activity was increased in the RA and SLE patients. We examined the effects of aspirin, sodium salicylate, auranofin, penicillamine, and corticosteroids on kinin metabolism, and all of these were marked inhibitors of ACE; however, only penicillamine had any demonstrable inhibition of carboxypeptidase. These observations suggest rapid degradation of DBK in patients with untreated RA and SLE, whereas drugs utilized in therapy have the opposite effects. Studies to examine the role of DBK in disease manifestations are in progress.