Assessment of the relationship between combinations of polymorphic variants of xenobiotic-metabolizing enzyme genes and predisposition to lung cancer

An imbalance between the phases of biotransformation systems, such as activation, detoxification, and release of toxic substances, is one of the causes of multifactor pathology. Therefore, it is important to examine the impact of the total contribution of the polymorphic variants of xenobiotic-metabolizing enzyme genes at all three phases on predisposition to lung cancer. The purposes of the present work were to study the relationship between polymorphic variants of xenobiotic-metabolizing enzyme genes and risk of lung cancer and to identify molecular genetic markers of predisposition to the disease. It was shown that GSTT1 null-genotype plays a dominant role in the development of lung cancer predisposition in the Belarusian population, while the polymorphic variants of other genes of xenobiotic-metabolizing enzymes render a modifying effect on predisposition to this disease. Combination 734AA CYP1A2/GSTT1(?)/GSTM1(+)/“slow” acetylator has the greatest risk significance, and combination GSTT1(?)/GSTM1(+)/“slow” acetylator exerts a protective effect.     

Association between plasma angiotensin-converting enzyme level and radiation pneumonitis

Angiotensin-converting enzyme (ACE) plays an important role in pulmonary fibrosis and may be involved in the development of radiation-induced lung damage. The objective of this study was to evaluate the predictive value of plasma ACE in radiation pneumonitis (RP). Patients with stage I-III lung cancer were treated with radiotherapy with or without chemotherapy. ACE levels were measured using enzyme-linked immunosorbent assay before radiotherapy (pre-RT) and when a median dose of 45 Gy (Range: 40-48 Gy) was reached (during-RT). The primary end point was > or = grade 2 RP. Statistic significances were evaluated with independent T-test and chi-square. Thirty-nine patients were enrolled in this study, among which 33.3% experienced > or = grade 2 RP. ACE levels, either pre-RT or during-RT, were significantly lower in the RP group than in the non-RP group (P=0.02 and 0.03, respectively). Nine out of the 19 patients (47.4%) with pre-RT ACE levels < or = 462 ng/mL experienced RP, versus 3 of 19 (15.8%) patients with ACE levels > 462 ng/mL (P=0.04). This study suggested that plasma ACE as a predictive factor for radiation pneumonitis deserves further study.     

A fluorometric assay for angiotensin-converting enzyme activity

A simple and sensitive assay for angiotensin-converting enzyme (ACE; EC 3.4.15.1) activity has been developed which employs fluorescently labeled tripeptides. ACE hydrolyzes dansylphenylalanyl-arginyl-tryptophan or dansyl-phenylalanyl-arginyl-phenylalanine, liberating dansyl-phenylalanine and a dipeptide. Dansyl-phenylalanine partitions quantitatively into chloroform, whereas the substrates are virtually insoluble in chloroform. This allows rapid measurement of ACE activity with high signal-to-noise ratios even when microliter aliquots of human serum are assayed. Inhibition studies of the dansyl-tripeptide cleaving activity of human serum and rat lung, the identity of the products of enzyme action, and the regional distribution of enzyme activity among rat tissues demonstrate that only ACE cleaves these substrates under the conditions employed here. This assay may be useful for the clinical measurement of human serum ACE activity and for research investigations of ACE from a variety of tissues.     

Correlation of endothelin-1 concentration and angiotensin-converting enzyme activity with the staging of liver fibrosis

Increased serum angiotensin-converting enzyme (SACE) activity and serum concentration of endothelin-1 (ET-1) were found in liver cirrhosis. We investigated a correlation between the different stages of liver fibrosis and SACE activity and serum ET-1 concentration. Seventy patients with pathohistologically established chronic liver disease were divided in three groups according to Ishak criteria for liver fibrosis: minimal fibrosis (Ishak score 0-1, n =20), medium fibrosis (Ishak score 2-5, n=20) and cirrhosis (Ishak score 6, n=30). SACE activity and ET-1 concentration were determined using commercial ELISA kits. SACE activity and ET-1 concentrations were proportional to the severity of disease, the highest being in patients with liver cirrhosis. Maximal increase in SACE activity was found between minimal and medium fibrosis while maximal increase in ET-1 concentration was revealed between medium fibrosis and cirrhosis. The analysis of the Receiver Operating Characteristic (ROC) curve for SACE activity suggested a cut-off value to separate minimal from medium fibrosis at 59.00 U/L (sensitivity 100%, specificity 64.7%). The cut-off value for serum ET-1 concentration to separate medium fibrosis from cirrhosis was 12.4 pg/mL (sensitivity 96.8%, specificity 94.4%). A positive correlation between SACE activity and ET-1 concentration was registered (Spearman's ? = 0.438, p = 0.004). Both SACE activity and ET-1 concentration were increased in all stages of liver fibrosis. Cut-off points for SACE activity and ET-1 concentration could be a biochemical marker for the progression of fibrosis. Positive correlation between SACE activity and ET-1 concentration might indicate their interaction in the development of liver cirrhosis.     

Method for determination of angiotensin-converting enzyme activity in blood and tissue by high-performance liquid chromatography

A simplified method for an angiotensin-converting enzyme activity assay in biological samples was developed. Samples were incubated with hippurylhistidylleucine, an artificial substrate of angiotensin-converting enzyme. The reaction was terminated by the addition of metaphosphoric acid and liberated hippuric acid in the supernatant was quantitated directly by reversed-phase high-performance liquid chromatography. Tissues were homogenized in the presence of Nonidet-P40, a detergent, and the resulting supernatant was used for the assay of tissue angiotensin-converting enzyme activity by high-performance liquid chromatography. The present procedure made it possible to determine angiotensin-converting enzyme activity in whole blood and the total activity in tissues. A comparative study of angiotensin-converting enzyme activity in plasma, kidney and lung of five experimental animals showed a high degree of variation from species to species.     

Substance P inhibition of the activity of the angiotensin-converting enzyme from human blood serum

Substance "P" (SP) and its derivatives inhibited activity of angiotensin-converting enzyme (ACE) in human blood serum, I50 for SP was 31 microM. The same results were obtained for N-terminal fragments of the SP molecule: Arg-Pro-Lys-Pro and Lys-Pro. The C-terminal heptapeptide and the dipeptide Arg-Pro negligibly inhibited ACE activity. A possible significance of the interaction between SP and ACE in the regulation of the microhemodynamics is discussed.     

A fluorescence-based protocol for quantifying angiotensin-converting enzyme activity

The determination of angiotensin-converting enzyme (ACE) activity represents a useful tool in the study of different health pathologies, such as hypertension. This protocol describes a fluorescent assay for measuring ACE activity in vitro with high precision and sensitivity. The method relies on the ability of ACE to hydrolyse the internally quenched fluorescent substrate o-aminobenzoylglycyl-p-nitro-L-phenylalanyl-L-proline. The generation of the fluorescent product o-aminobenzoylglycine can be continuously monitored, preferably using a microtiter-plate fluorometer, though the use of a conventional cuvette fluorometer would also be possible. The method has important advantages with respect to other assays, because it involves only a one-step reagent, is easy to carry out and allows the analysis of an elevated number of samples in shorter times. It can be completed in one and a half hours. In addition, the fact that all reagents are commercially available allows the rapid introduction of the assay into the laboratory.     

New human V beta genes and polymorphic variants.

To extend the characterization of the human V beta gene repertoire, we utilized anchored or V beta-specific polymerase chain reaction to generate a large (approximately 200 clones) beta-chain library from the thymus of a single individual. Nine new V beta genes were identified, including single members for two new subfamilies (V beta 22 and 23), two new members of the V beta 5 subfamily, and one new member each for V beta 2, 6, 7, 9, and 12. Full-length sequences were also obtained for the published partial sequences of V beta 3, 5.3, 9.1, and 13.4, and additional nucleotides for V beta 7.1 and V beta 7.2. Based on consensus sequences from multiple clones, apparent allelic variants for six V beta genes (V beta 2.1, 5.3, 7.2, 8.2, 13.4, and 16) were also tentatively identified. Population and family studies for two of these (V beta 2.1 and 16) further confirmed that these V beta were alleles and not separate genes. Nonconservative substitutions in some of these alleles, as well as in previously identified alleles, are located at the hypervariable loops or the framework region. These findings indicate that V beta gene polymorphism appears to be significant in humans and might be the result of selective pressure imposed by conventional Ag (hypervariable loops) or superantigens (framework regions).     

Elevated plasma homocysteine elicits an increase in antioxidant enzyme activity

Elevated plasma homocysteine is considered to be a risk factor for cardiovascular disease. The mechanisms for this effect are not fully understood but there is some evidence for a role for reactive oxygen species (ROS). This study was conducted to explore the effects of elevated plasma total homocysteine (tHcy) concentration on activity of antioxidant enzymes in the circulation. The study group consisted of 10 patients with inherited defects of homocysteine metabolism, from whom 41 blood samples were collected over a period of six months. Blood samples were also collected from 13 of their obligate heterozygous parents. For data analysis samples were classified as those with plasma tHcy < 20 microM or > 20 microM. The activity of erythrocyte superoxide dismutase (SOD) and plasma glutathione peroxidase (GSHPx) was elevated in samples with plasma tHcy > 20 microM. Moreover, a significant correlation was demonstrated between plasma GSHPx activity, plasma glutathione peroxidase protein and plasma tHcy. III vitro studies confirmed that this observation was not due to a simple chemical enhancement of enzyme activity. Homocysteine protected GSHPx from loss of activity following incubation at 37 degrees C. A similar effect was seen with another thiol-containing amino acid, cysteine. Results suggest that elevated plasma tHcy represents an oxidative stress, resulting in an adaptive increase in activity of antioxidant enzymes in the circulation.     

Elevated plasma homocysteine elicits an increase in antioxidant enzyme activity

Elevated plasma homocysteine is considered to be a risk factor for cardiovascular disease. The mechanisms for this effect are not fully understood but there is some evidence for a role for reactive oxygen species (ROS). This study was conducted to explore the effects of elevated plasma total homocysteine (tHcy) concentration on activity of antioxidant enzymes in the circulation. The study group consisted of 10 patients with inherited defects of homocysteine metabolism, from whom 41 blood samples were collected over a period of six months. Blood samples were also collected from 13 of their obligate heterozygous parents. For data analysis samples were classified as those with plasma tHcy < 20 μM or ≥ 20 μM. The activity of erythrocyte superoxide dismutase (SOD) and plasma glutathione peroxidase (GSHPx) was elevated in samples with plasma tHcy > 20 μM. Moreover, a significant correlation was demonstrated between plasma GSHPx activity, plasma glutathione peroxidase protein and plasma tHcy. In vitro studies confirmed that this observation was not due to a simple chemical enhancement of enzyme activity. Homocysteine protected GSHPx from loss of activity following incubation at 37°C. A similar effect was seen with another thiol-containing amino acid, cysteine. Results suggest that elevated plasma tHcy represents an oxidative stress, resulting in an adaptive increase in activity of antioxidant enzymes in the circulation.     

Seasonal variations in antioxidant enzyme activity in ram seminal plasma

Seminal oxidative stress status is emerging as a significant prognostic tool in assisted reproductive technology. A dynamic interplay between pro- and anti-antioxidant substances in the ejaculate is essential. In this study, we determined seasonal changes in the activity of the antioxidant enzyme defense system comprising superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPx) and catalase (CAT) in seminal plasma (SP) of mature Rasa Aragonesa rams. This breed corresponds to a local Spanish genotype with a short seasonal anoestrus between May and July. In addition, the activity of these enzymes was measured in protein fractions isolated from ram SP by exclusion chromatography. Total protein content in ram SP was higher during the breeding season (October-February) with a significantly higher value in first ejaculates. Antioxidant enzyme activities were higher during the non-breeding season (March-September). Comparing first and second ejaculates, SOD and CAT activities were higher in the first of all months. However, GR and GPx activities changed throughout the year. Thus, GR activity was higher in July and August in first ejaculates, this difference being significant in July (4.53 versus 2.37 nmol substrate/minmg protein, P<0.05). Conversely, GPx activity was significantly higher in September and November in second ejaculates (21.1 versus 6.81 and 10.91 versus 5.33, respectively, P<0.05). After SP fractionation by exclusion chromatography, GR activity was located in fractions 1 and 2 being irrelevant in the following peaks, and CAT activity was not detected all along the chromatographic profile. GPx and SOD activities were spread out along all fractions with a main peak in fractions 6 and 7. Given that these two fractions showed the greatest capacity to recover and prevent cold-shock membrane injury [Barrios B, Pérez-Pé R, Gallego M, Tato A, Osada J, Muino-Blanco T, Cebrián-Pérez JA. Seminal plasma proteins revert the cold-shock damage on ram sperm membrane. Biol Reprod 2000;63:1531-7, Barrios B, Fernández-Juan M, Muino-Blanco T, Cebrián-Pérez J. Immunocytochemical localization and biochemical characterization of two seminal plasma proteins that protect ram spermatozoa against cold shock. J Androl 2005;26:539-49], we could suggest that the protective effect might be, at least partially, due to the antioxidant enzyme activity.     

Chromatographic determination of angiotensin-converting enzyme and angiotensinase activity

An analytical method utilizing an automatic amino acid analyzer is described for the separation, identification, and measurement of 5 to 50 nmol of angiotensin I, angiotensin II, [Des-Phe⁸]angiotensin II, Phe-His-Leu, His-Leu, isoleucine, leucine, tyrosine, and phenylalanine. Aminex A-5 cation-exchange resin (0.9 × 15 cm) is sequentially eluted with three sodium citrate buffers: pH 3.25, 0.2 n; pH 4.85, 0.54 n, and pH 6.5, 0.39 n at 60 and 80°C. Reaction with ninhydrin is used for detection. This chromatographic system was used to determine angiotensin-converting enzyme activity and the angiotensinase activity of rabbit brain endopeptidase B. In each assay, the unhydrolyzed substrate and both products were measured simultaneously in one step without pretreatment of the hydrolysate. Products were recovered in 1:1 molar ratios and the overall recovery of unhydrolyzed substrate of products was quantitative.     

Isolation of angiotensin-converting enzyme inhibitor from porcine plasma

An inhibitory peptide of angiotensin-converting enzyme was purified from porcine plasma. The final preparation showed IC50 values of 4.2, 0.6, and 0.9 microgram/ml for angiotensin-converting enzymes from guinea pig serum, rabbit lung, and monkey brain, respectively. The amino acid sequence of the inhibitor was determined as leucyl-valyl-leucine by Edman procedure. This structural observation was supported by mass spectrometric analysis.     

Correlation between plasma membrane surface area and transferrin secretion rate in isolated hepatocytes

It is generally considered that in exocytosis the size of the secreting cells does not increase when the membranes of exocytosis vesicles fuse with the plasma membrane. As the factors involved in the regulation of this phenomenon are poorly understood, we thought it worthwhile to investigate the relationship between the plasma membrane surface area and secretory activity. Isolated rat hepatocytes were prepared by liver collagenase perfusion. Secretion of the plasma protein, transferrin (Tf) was detected at the single cell level with specific anti-rat transferrin antibodies using the reverse hemolytic plaque test. Hepatocyte surface and hemolytic ring surface areas were calculated from diameters of hepatocyte and hemolytic plaque measured after 5h of incubation. A highly significant correlation was established between the plaque-forming hepatocyte surface areas and the corresponding hemolytic surface areas. This result was confirmed using an automatic image analysis method. Two-month-old rats were compared to 4-month-old rats. We observed that the ratio of the quantity of transferrin secreted by hepatocytes to the hepatocyte surface area was constant for a given incubation time, whatever the size of the hepatocytes. These results suggest that the plasma membrane surface area of hepatocytes may constitute a limiting factor in Tf secretion.     

Characterization and activity of angiotensin-converting enzyme in Holstein semen

The study was designed to perform immunodetection in spermatozoa and seminal plasma, immunolocalization in spermatozoa, and evaluation of the enzymatic activity of angiotensin-converting enzyme (ACE) in the semen of Holstein bulls. We used ejaculates from five bulls as part of a regular collection of semen. The monoclonal anti-ACE antibody recognized a single protein band with 100 kDa in detergent extract prepared from sperm and in seminal plasma. ACE enzymatic activity in sperm was 43.7, 21.3, 45.6, 60.0, and 57.7 mU/mL in bulls 1, 2, 3, 4, and 5, respectively, and 0.3, 2.3, 3.0, 2.3, and 2.6 mU/mL in seminal plasma of the same bulls, respectively. The average percentages of sperm with acrosome reactions after treatment with heparin were 28.3%, 28.6%, 35.2%, 25.0%, and 32.3%, respectively. These values were higher than the percentages of acrosome reactions in controls and the captopril group (P<0.05), although no difference was seen between the captopril and control groups (P>0.05). After 4h of incubation, motility in the control group (32.9%) was significantly higher than that in the heparin (15.7%) and captopril (12.1%) groups. No difference was found in motility after the capacitation assay in the heparin and captopril groups (P>0.05). In conclusion, ACE was immunologically localized in the acrosome of the spermatozoa of Holstein bull, the specific enzymatic activity of ACE in detergent-extracted spermatozoa and seminal plasma was inhibited by captopril, and this ACE inhibitor reduced the percentage of sperm with progressive motility and acrosome reactions after capacitation in vitro.     

Radioenzymatic assay of angiotensin-converting enzyme inhibitors in plasma and urine

A rapid, sensitive assay for angiotensin-converting enzyme (ACE) inhibitors is described. Biological samples were diluted with methanol to precipitate endogenous ACE and centrifuged. Supernatants were further diluted with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer, pH 8. Diluted samples were incubated at 37 degrees C with the substrate [3H]hippurylglycylglycine and rabbit lung ACE for 45 min. Acid (1.0 N HCl) was then added, and the product, [3H]hippuric acid, was extracted into a water-immiscible scintillation cocktail. Drug standards were prepared in the biological matrix to correct for drug recovery. A computer program was used to convert radioactivity (dpm) to units of enzyme activity and then correlate enzyme activity with drug concentration. The ester prodrugs fosenopril and enalapril could be assayed down to 4 ng/ml in plasma after ester hydrolysis with NaOH. Drug disposition studies in rats, dogs, and monkeys have demonstrated that the method can be readily adapted to any ACE inhibitor and is suitable for determining drug bioavailability and pharmacokinetics.     

Determination of angiotensin-converting enzyme activity using dansyl-Phe-Ala-Arg as the substrate

Modificated method for the determination of the angiotensin converting enzyme (EC 3.4.15.1) activity in neural tissue is proposed. The methods is based on fluorimetrically determination of released dansyl-Phe from dansyl-Phe-Ala-Arg at pH 7.6. Km is 50 +/- 10 MM. The high specificity of the method is provide by using captopril, the high specific angiotensin converting enzyme inhibitor. The sensitivity of the method is 0.001 nmol/min per mg protein that it is lesser in 15-fold than the lowest enzyme activity in brain region. The distribution of the angiotensin converting enzyme activity that using the method in brain regions and peripherial tissues of rat is presented.     

Linkage between genes for coat colour and for blood plasma esterase in dogs

A study on linkage in dogs has been made on the basis of comparable studies in other mammal species. In a breeding experiment one dog was mated to 14 bitches. The dog was heterozygous for the plasma esterase locus (Es-1) and the extension locus (E) for coat colour. The 14 bitches, homozygous for both loci, produced a total of 96 offspring. The recombination distance between the loci is calculated to be 34.4 +/- 4.8 cM. The basis for homology between species for the two loci has been discussed.     

Age-related changes in blood plasma antioxidant activity in population of the southern Altai

The blood plasma antioxidant activity was studied in the Russian and Kazakh aborigines of the southern Altai low and high mountains. There was established a decrease of the blood plasma antioxidant activity with age and a relatively low plasma antioxidant activity in the mid-mountain population; in its senior age groups, the gender differences of this parameter were revealed.