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Tepel M. Acetylcysteine for the prevention of radiocontrast -induced nephropathy. Minerva Cardioangiol 2003; 51:525-30. [PMID: 14551521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
Radiocontrast-induced nephropathy is the 3rd most common cause of in-hospital acute renal failure after hypotension and surgery. Radio-graphic contrast media are used at a progressive rate for several diagnostic and therapeutic applications. Prevention of radiocontrast-induced nephropathy will become more important, including risk of patient impairment and costs. Radiocontrast-induced ne-phropathy is due to vasoconstriction-mediated renal medullary ischemia and direct toxic damage to renal tubular epithelial cells. These effects may in part be mediated by generation of reactive oxygen species. Several prospective, randomized, placebo-controlled studies in patients with moderate renal insufficiency showed that the prophylactic oral administration of acetylcysteine at a dose of 600 mg twice daily along with hydration prevents the reduction in renal function after radiocontrast administration. Recently, intravenous administration of acetyl-cysteine has also been shown to be effective. Use of acetylcysteine together with hydration is the treatment of choice to prevent radiocontrast-induced nephropathy.
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Jankowski J, van der Giet M, Jankowski V, Schmidt S, Hemeier M, Mahn B, Giebing G, Tölle M, Luftmann H, Schlüter H, Zidek W, Tepel M. Increased plasma phenylacetic acid in patients with end-stage renal failure inhibits iNOS expression. J Clin Invest 2003. [DOI: 10.1172/jci200315524] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Jankowski J, van der Giet M, Jankowski V, Schmidt S, Hemeier M, Mahn B, Giebing G, Tolle M, Luftmann H, Schluter H, Zidek W, Tepel M. Increased plasma phenylacetic acid in patients with end-stage renal failure inhibits iNOS expression. J Clin Invest 2003; 112:256-64. [PMID: 12865413 PMCID: PMC164281 DOI: 10.1172/jci15524] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2002] [Accepted: 05/13/2003] [Indexed: 11/17/2022] Open
Abstract
NO prevents atherogenesis and inflammation in vessel walls by inhibition of cell proliferation and cytokine-induced endothelial expression of adhesion molecules and proinflammatory cytokines. Reduced NO production due to inhibition of either eNOS or iNOS may therefore reinforce atherosclerosis. Patients with end-stage renal failure show markedly increased mortality due to atherosclerosis. In the present study we tested the hypothesis that uremic toxins are responsible for reduced iNOS expression. LPS-induced iNOS expression in mononuclear leukocytes was studied using real-time PCR. The iNOS expression was blocked by addition of plasma from patients with end-stage renal failure, whereas plasma from healthy controls had no effect. Hemofiltrate obtained from patients with end-stage renal failure was fractionated by chromatographic methods. The chromatographic procedures revealed a homogenous fraction that inhibits iNOS expression. Using gas chromatography/mass spectrometry, this inhibitor was identified as phenylacetic acid. Authentic phenylacetic acid inhibited iNOS expression in a dose-dependent manner. In healthy control subjects, plasma concentrations were below the detection level, whereas patients with end-stage renal failure had a phenylacetic acid concentration of 3.49 +/- 0.33 mmol/l (n = 41). It is concluded that accumulation of phenylacetic acid in patients with end-stage renal failure inhibits iNOS expression. That mechanism may contribute to increased atherosclerosis and cardiovascular morbidity in patients with end-stage renal failure.
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Abstract
BACKGROUND Angiotensin-converting enzyme inhibitors may affect reactive oxygen species in humans in vitro and in vivo. In the present study we evaluated whether angiotensin-converting enzyme inhibitors may affect NAD(P)H oxidase activity. MATERIALS AND METHODS The production of reactive oxygen species was measured spectrophotometrically in mononuclear leukocytes using the fluorescent dye, dichlorofluorescein diacetate. The effects of quinaprilat, captopril, enalaprilat and lisinopril on phorbol myristate acetate-induced reactive oxygen species generation were investigated in vitro. The effects of quinaprilat, captopril, enalaprilat and lisinopril on the NAD(P)H oxidase activity of the mononuclear leukocytes were measured photometrically. In addition, reactive oxygen species were measured before and 4 h after oral administration of quinapril. RESULTS In vitro, the addition of quinaprilat (72 +/- 6% of control; mean +/- SEM; n= 19; P < 0.001) and captopril (48 +/- 2% of control; n= 19; P < 0.001) significantly reduced the phorbol-12-myristate-13-acetate-induced reactive oxygen species generation by the mononuclear leukocytes, whereas enalaprilat and lisinopril showed no effect. The effect of captopril on phorbol-12-myristate-13-acetate-induced reactive oxygen species generation in vitro was concentration-dependent. Quinaprilat and captopril significantly inhibited the NAD(P)H oxidase activity. After the oral administration of 10 mg of quinapril the phorbol-12-myristate-13-acetate-induced reactive oxygen species generation by the mononuclear leukocytes was significantly decreased from 1981 +/- 292% to 988 +/- 141% (n = 14; P < 0.01). CONCLUSION Quinapril and captopril decrease the production of reactive oxygen species.
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Abstract
Radiocontrast nephropathy may in part be mediated by generation of reactive oxygen species causing direct toxic damage to renal tubular epithelial cell and renal medullary ischemia. Data from experimental studies indicated that antioxidants, eg, acetylcysteine, may prevent radiocontrast-induced nephropathy. Recently, one prospective, randomized, placebo-controlled study in patients with moderate renal insufficiency confirmed that the prophylactic oral administration of acetylcysteine at a dose of 600 mg twice daily along with hydration prevents the reduction in renal function by a nonionic, low-osmolality radiocontrast agent.
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Chen T, Kao MY, Tepel M, Rush J, Church GM. A dynamic programming approach to de novo peptide sequencing via tandem mass spectrometry. J Comput Biol 2001; 8:325-37. [PMID: 11535179 DOI: 10.1089/10665270152530872] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Tandem mass spectrometry fragments a large number of molecules of the same peptide sequence into charged molecules of prefix and suffix peptide subsequences and then measures mass/charge ratios of these ions. The de novo peptide sequencing problem is to reconstruct the peptide sequence from a given tandem mass spectral data of k ions. By implicitly transforming the spectral data into an NC-spectrum graph G (V, E) where /V/ = 2k + 2, we can solve this problem in O(/V//E/) time and O(/V/2) space using dynamic programming. For an ideal noise-free spectrum with only b- and y-ions, we improve the algorithm to O(/V/ + /E/) time and O(/V/) space. Our approach can be further used to discover a modified amino acid in O(/V//E/) time. The algorithms have been implemented and tested on experimental data.
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Tepel M, van der Giet M, Zidek W. Efficacy and tolerability of angiotensin II type 1 receptor antagonists in dialysis patients using AN69 dialysis membranes. Kidney Blood Press Res 2001; 24:71-4. [PMID: 11174010 DOI: 10.1159/000054209] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
AIMS AND METHODS Our aim was to evaluate the antihypertensive efficacy and tolerability of angiotensin II type 1 (AT1) receptor antagonists. Valsartan or candesartan cilexetil was administered to 11 dialysis patients with elevated blood pressure. The patients (6 male, 5 female; mean age +/- SD 61+/-11 years) were on regular bicarbonate hemodialysis three times weekly for more than 3 months using acrylonitrile and sodium methallyl sulfonate copolymer (AN69) dialysis membranes. RESULTS Within 252 days after administration of the AT1 receptor antagonists the systolic blood pressure was significantly reduced from 161+/-13 to 130+/-12 mmHg (p<0.001), whereas the diastolic blood pressure did not change significantly (76+/-8 vs. 71+/-8 mmHg; p>0.05). In addition, heart rate (75+/-7 vs. 80+/-8/min), body weight, and laboratory variables (hemoglobin, creatinine, blood urea nitrogen, serum potassium, serum sodium, serum calcium, and total protein) showed no significant changes. During 1,188 hemodialysis sessions using AN69 membranes, no hypersensitivity reactions occurred after administration of AT1 receptor antagonists. CONCLUSION The results indicate that once-daily administration of AT1 receptor antagonists efficiently reduces the systolic blood pressure in hemodialysis patients.
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Jankowski J, Hagemann J, Tepel M, van Der Giet M, Stephan N, Henning L, Gouni-Berthold I, Sachinidis A, Zidek W, Schluter H, Gouni-Berthold H. Dinucleotides as growth-promoting extracellular mediators. Presence of dinucleoside diphosphates Ap2A, Ap2G, and Gp2G in releasable granules of platelets. J Biol Chem 2001; 276:8904-9. [PMID: 11115507 DOI: 10.1074/jbc.m009527200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dinucleoside diphosphates, Ap(2)A, Ap(2)G, and Gp(2)G represent a new class of growth-promoting extracellular mediators, which are released from granules after activation of platelets. The presence of theses substances was shown after purification from a platelet concentrate. The substances were identified by UV spectrometry, retention time comparison with authentic substances, matrix-assisted laser desorption/ionization mass spectrometry, post-source-decay matrix-assisted laser desorption/ionization mass spectrometry, and enzymatic analysis. Ap(2)A, Ap(2)G, and Gp(2)G have growth-stimulating effects on vascular smooth muscle cells in nanomolar concentrations as shown by [(3)H]thymidine incorporation measurements. The calculated EC(50) (log m; mean +/- S.E.) values were -6.07 +/- 0.14 for Ap(2)A, -6.27 +/- 0.25 for Ap(2)G, and -6.91 +/- 0.44 for Gp(2)G. At least 61.5 +/- 4.3% of the dinucleoside polyphosphates are released by platelet activation. The intraplatelet concentrations suggest that, in the close environment of a platelet thrombus, similar dinucleoside polyphosphate concentrations can be found as in platelets. Intraplatelet concentration can be estimated in the range of 1/20 to 1/100 of the concentration of ATP. In conclusion, Ap(2)A, Ap(2)G, and Gp(2)G derived from releasable granules of human platelets may play a regulatory role in vascular smooth muscle growth as growth-promoting mediators.
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Henning BF, Zidek W, Riezler R, Graefe U, Tepel M. Homocyst(e)ine metabolism in hemodialysis patients treated with vitamins B6, B12 and folate. RESEARCH IN EXPERIMENTAL MEDICINE. ZEITSCHRIFT FUR DIE GESAMTE EXPERIMENTELLE MEDIZIN EINSCHLIESSLICH EXPERIMENTELLER CHIRURGIE 2001; 200:155-68. [PMID: 11426667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
Hyperhomocyst(e)inemia is commonly accepted as an independent atherosclerotic risk factor. In most hemodialysis patients, serum homocyst(e)ine is markedly elevated and may contribute to premature atherosclerosis in these patients. Whereas the beneficial effect of folate supplementation on serum homocyst(e)ine has been extensively studied, there are less detailed studies on the effects of cobalamin and pyridoxal phosphate alone, or in combination with folate. We examined the effect of a four-week course of intravenous treatment with folate (1.1 mg), cobalamin (1.0 mg), and pyridoxal phosphate (5.0 mg), administered once (group 1), twice (group 2) or thrice (group 3) weekly in 33 hemodialysis patients divided in three groups of 11 patients. All patients were followed for a further four weeks after treatment was stopped. Serum homocyst(e)ine, cobalamin, folate and pyridoxal phosphate, as well as the metabolites of homocyst(e)ine, methylmalonate, 2-methylcitrate and cystathionine, were determined before, during and after treatment. Baseline serum homocyst(e)ine correlated significantly with serum folate (P=0.0149), cobalamin (P=0.0047) and pyridoxal phosphate (P=0.0408). Correlations independent from the other metabolites or vitamins were found for methylmalonate (P=0.003) and folate (P=0.029). All regimens increased serum cobalamin significantly (in group 1 from 444 +/- 215 to 17,303 +/- 11,989 pg/ml, P<0.01; in group 2 from 542 +/- 633 to 44,896 +/- 15,772 pg/ml, P<0.001; in group 3 from 548 +/- 394 to 77,961 +/- 31,546 pg/ml, P<0.001), but did not increase any of the other vitamin levels. Serum homocyst(e)ine was lowered significantly by 39.8% +/- 31.9% (P<0.05) with two and by 30.1% +/- 26.9% (P<0.05) with three vitamin dosages weekly, but not with one dosage weekly. Since methylmalonate is known to be a sensitive marker of cobalamin deficiency, the data support an important influence of cobalamin levels on baseline homocyst(e)ine levels. Increasing cobalamin levels and additional treatment with folate and pyridoxal phosphate 156 may decrease serum homocyst(e)ine in the same way as high doses of folate alone.
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Jankowski J, Hagemann J, Yoon MS, van der Giet M, Stephan N, Zidek W, Schlüter H, Tepel M. Increased vascular growth in hemodialysis patients induced by platelet-derived diadenosine polyphosphates. Kidney Int 2001; 59:1134-41. [PMID: 11231371 DOI: 10.1046/j.1523-1755.2001.0590031134.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Enhanced vascular smooth muscle cell (VSMC) growth is one hallmark of atherosclerosis. One mechanism responsible for stimulating arterial smooth muscle cell growth is the release of growth factors from platelets aggregating at endothelial lesions. Since in end-stage renal failure (ESRF) atherogenesis is markedly accelerated, the release of VSMC growth factors on aggregation of platelets from hemodialysis patients, ESRF patients in the predialysis stage, and healthy subjects was examined. METHODS Platelets were activated by thrombin, and the supernatant was tested for growth stimulation in VSMCs from rat aorta. The cell proliferation rate was determined by [(3)H]-thymidine incorporation in VSMCs. The diadenosine polyphosphate (Ap(n)A with N = 3 to 6) content in the supernatant and in intact platelets was determined using a chromatographic assay established on the basis of affinity- and reversed-phase chromatographic methods. RESULTS The thrombin-activated platelet supernatant from hemodialysis patients (N = 15) increased the [(3)H]-thymidine incorporation rate in VSMC s in comparison to the supernatant of healthy control subjects (N = 17, counts/supernatant of 10(6) stimulated platelets +/- SEM, 604 +/- 71 vs. 364 +/- 45, P < 0.05). The addition of the selective P2-receptor blocker pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid to supernatants inhibited the stimulatory effects of Ap(n)A on the growth of vascular smooth muscle cells (219 +/- 53 vs. 156 +/- 71 counts/supernatant of 106 stimulated platelets +/- SEM). The Ap(n)A (N = 3 to 6) amount of thrombin-activated platelet supernatants from hemodialysis patients was significantly higher than in platelets from 10 healthy control subjects (Ap(3)A, 119 +/- 32 vs. 12 +/- 3; Ap(4)A, 154 +/- 59 vs. 43 +/- 20; Ap(5)A, 39 +/- 14 vs. 13 +/- 6; Ap(6)A, 42 +/- 19 vs. 2 +/- 1 fg/platelet +/- SEM, each P < 0.05, N = 10). The intracellular Ap(n)A (N = 3 to 6) amount of intact platelets from hemodialysis patients (N = 61) was significantly higher than that from healthy control subjects [N = 30, Ap(n)A amount (fg/platelet +/- SEM): Ap(3)A, 366 +/- 68 vs. 14.7 +/- 1; Ap(4)A, 336 +/- 48 vs. 19 +/- 2; Ap(5)A, 227 +/- 35 vs. 10 +/- 1; Ap(6)A, 141 +/- 45 vs. 4 +/- 1; each P < 0.01]. CONCLUSIONS The increased amount of dinucleoside polyphosphate in platelets from hemodialysis patients may be an important additional atherogenic factor.
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Tepel M, Zidek W. Insulin, blood pressure and elevated Na+/H+ exchange activity--novel therapeutic implications. Eur J Clin Invest 2001; 31:189. [PMID: 11264643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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Orie NN, Zidek W, Tepel M. Increased intracellular generation of reactive oxygen species in mononuclear leukocytes from patients with diabetes mellitus type 2. Exp Clin Endocrinol Diabetes 2001; 108:175-80. [PMID: 10926312 DOI: 10.1055/s-2000-7740] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Since increased cellular production of reactive oxygen species is a source of oxidative stress and thus may contribute to the development of diabetic complications, the baseline and stimulated concentrations of intracellular reactive oxygen species were measured in 16 patients with diabetes mellitus type 2 and 19 healthy control subjects. Reactive oxygen species and cytosolic calcium were monitored spectrophotometrically using dihydrorhodamine-123 and fura-2, respectively, in a suspension of mononuclear leukocytes. Measurements were made in the presence or absence of superoxide dismutase, sodium azide, genistein, or bisindolylmaleimide 1. Baseline reactive oxygen species concentrations were significantly higher in diabetic patients compared with control (p<0.001). Activation of mononuclear leukocytes by formyl-Met-Leu-Phenylalanine and phytohemagglutinin significantly increased reactive oxygen species in diabetic patients compared with control (p<0.05). The formyl-Met-Leu-Phenylalanine-induced increases were unchanged in the presence of superoxide dismutase, but dropped significantly in the presence of sodium azide by 80% and 73% in diabetic patients and control, respectively (each p<0.01). The formyl-Met-Leu-Phenylalanine-induced responses were significantly inhibited by genistein and bisindolylmaleimide 1 (p<0.01), suggesting the involvement of tyrosine kinase and protein kinase C. Resting calcium (p<0.05) and stimulated calcium were significantly greater in diabetic patients than in control. The results show that patients with diabetes mellitus type 2 generate increased reactive oxygen species under stimulated conditions, suggesting increased risk for oxidative stress and associated complications.
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Jankowski J, Tepel M, Stephan N, van der Giet M, Breden V, Zidek W, Schlüter H. Characterization of p-hydroxy-hippuric acid as an inhibitor of Ca2+-ATPase in end-stage renal failure. KIDNEY INTERNATIONAL. SUPPLEMENT 2001; 78:S84-8. [PMID: 11168989 DOI: 10.1046/j.1523-1755.2001.59780084.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Characterization of p-hydroxy-hippuric acid as an inhibitor of Ca2+-ATPase in end-stage renal failure. In patients with end-stage renal failure (ESRF), disturbances of Ca2+ metabolism are common. Besides hormonal changes, inhibition of cellular Ca2+-ATPase was postulated to contribute to uremic toxicity. We purified a potent inhibitor of the Ca2+-ATPase from the ultrafiltrate of patients with ESRF by multiple steps of high-performance liquid chromatography to homogeneity, and identified the isolated inhibitor by mass spectrometric methods as p-hydroxy-hippuric acid. The enzyme used for the Ca2+-ATPase assay system was isolated from red blood cells by cross-flow filtration. The activity of the Ca2+-ATPase was measured spectrophotometrically as the difference in hydrolysis of adenosine 5'-triphosphate (ATP) in the presence and absence of Ca2+ with different concentrations of ATP and p-hydroxyhippuric acid. The Ca2+-ATPase was found to be inhibited by p-hydroxy-hippuric acid at a concentration above 11.7 micromol/L. p-Hydroxyhippuric acid inhibited the erythrocyte Ca2+-ATPase by reducing Vmax and increasing the Km value. The EC50 (log mol/L; mean +/- SEM) for p-hydroxy-hippuric acid was calculated as 4.82 +/- 0.14. In conclusion, p-hydroxy-hippuric acid may play a role in disturbed Ca2+ metabolism in end-stage renal failure.
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van der Giet M, Schmid A, Jankowski J, Schlüter H, Zidek W, Tepel M. CoenzymeA glutathione disulfide is a potent modulator of angiotensin II-induced vasoconstriction. Am J Hypertens 2001; 14:164-8. [PMID: 11243308 DOI: 10.1016/s0895-7061(00)01237-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CoenzymeA glutathione disulfide (CoASSG) has recently been isolated from bovine adrenal glands and is assumed to play an important role in blood pressure (BP) control. We used the isolated perfused rat kidney to investigate the modulating effects of CoASSG on angiotensin II (AngII)-induced vasoconstriction. Permanent perfusion with CoASSG (1 micromol/L) for 60 min induced a significant (P < .05) shift to the left in the dose-response curve for AngII (about 3.1-fold), whereas the dose-response curve for norepinephrine (NE) was unaffected. During continuous perfusion with 1 micromol/L CoASSG, the repetitive application of 10 pmol AngII significantly increased its vasoconstriction by 170% +/- 14% (P < .05) and 235% +/- 50% (P < .05) for 60 and 120 min, respectively. The potentiation of AngII by permanent perfusion with CoASSG is dose- and time-dependent and shows a plateau at 120 min. Glutathione, oxidized coenzymeA, and coenzymeA (each 1 micromol/L) are not able to enhance the vasoconstriction induced by AngII. We conclude that CoASSG is able to potentiate the vasoactive properties of AngII, and that CoASSG might play an important role in BP regulation via modulating effects of AngII.
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Henning BF, Tepel M, Riezler R, Naurath HJ. Long-term effects of vitamin B(12), folate, and vitamin B(6) supplements in elderly people with normal serum vitamin B(12) concentrations. Gerontology 2001; 47:30-5. [PMID: 11244289 DOI: 10.1159/000052767] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND In the elderly, deficiencies of folate, cobalamin (vitamin B(12)) and pyridoxal phosphate (vitamin B(6)) are common. The metabolites homocysteine, methylmalonic acid, 2-methylcitric acid and cystathionine have been reported to be sensitive markers of these vitamin deficiencies. OBJECTIVE The long-term (269 days) effect of an intramuscular vitamin supplement containing 1 mg vitamin B(12), 1.1 mg folate, and 5 mg vitamin B(6) on serum concentrations of homocysteine (tHcy), methylmalonic acid (MMA), 2-methylcitric acid (2-MCA), and cystathionine (Cysta) was studied in 49 elderly subjects with normal levels of vitamin B(12). METHODS Vitamin supplement was administered 8 times over a 21-day period, metabolite concentrations were measured until day 269 (e.g. 248 days after the end of vitamin supplementation). RESULTS From day 0 to 21, the serum levels of the 3 vitamins increased significantly, after cessation of supplementation the levels returned to baseline within the follow-up period. The MMA, 2-MCA and tHcy levels decreased during the treatment period significantly and did not reach baseline values within the 248-day period. Cysta levels did not differ significantly from baseline, either during or after treatment. CONCLUSION MMA and 2-MCA levels rather reflect the availability of vitamins, especially cobalamin, than the actual serum levels. Since deficiencies of folate, cobalamin and pyridoxal phosphate in the elderly may cause hyerhomocysteinemia and hence may have unfavorable effects on mental performance, determination of MMA and 2-MCA levels in elderly patients with mental disturbances may be a cost-effective measure to improve or maintain mental performance.
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van der Giet M, Westhoff T, Cinkilic O, Jankowski J, Schlüter H, Zidek W, Tepel M. The critical role of adenosine and guanosine in the affinity of dinucleoside polyphosphates to P(2X)-receptors in the isolated perfused rat kidney. Br J Pharmacol 2001; 132:467-74. [PMID: 11159696 PMCID: PMC1572568 DOI: 10.1038/sj.bjp.0703817] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The activation of P(2x)-receptors in the rat renal vasculature by dinucleoside polyphosphates with variable phosphate group chain length (Xp(n)X; X=Adenin (A) /Guanin (G), n=4 - 6) was studied by measuring their effects on perfusion pressure of the isolated perfused rat kidney at constant flow in an open circuit. 2. Like Ap(4)A, Ap(5)A and Ap(6)A the dinucleoside polyphosphates Ap(4)G, Ap(5)G and Ap(6)G exerted a vasoconstriction which could be blocked by suramin and pyridoxal-phosphate-6-azophenyl-2; 4-disulphonic acid (PPADS). 3. Gp(4)G, Gp(5)G and Gp(6)G showed only very weak vasoconstriction at high doses. 4. Ap(6)A and alpha, beta-meATP could not be blocked by the selective P(2x1)-receptor antagonisten NF023 (30 microM), whereas Ap(4)A, Ap(4)G, Ap(5)A, Ap(5)G and Ap(6)G were partially blocked by NF023. 5. Inhibition of endothelial NO-synthase by N(omega)-nitro-L-arginine methyl ester (L-NAME) did not affect vasoconstrictions induced by dinucleosidepolyphosphates. 6. P(2x)-receptor can only be activated if at least one adenosine moiety is present in the molecule. 7. Ap(n)G show a weaker vasoconstrictive action than corresponding Ap(n)A, concluding that two adenosine moieties enhance the P(2x)-receptor binding and activation. 8. Xp(n)X containing five phosphate groups show the most pronounced vasoconstrictive effect whereas four phosphate groups show the less effect, therefore the number of phosphate groups critically changes receptor affinity. 9. Additional experiments using permanent perfusion with alpha, beta-methylene ATP (alpha,beta-meATP) and the selective P(2x1)-receptor antagonist NF023 showed that the newly discovered human dinucleoside polyphosphates activated the vascular P(2x1)-receptor and an recently identified new P(2x)-receptor subtype. 10. The differential effects of dinucleoside polyphosphates allow a fine tuning of local perfusion via composition of Xp(n)Xs.
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Nofer JR, Fobker M, Höbbel G, Voss R, Wolinska I, Tepel M, Zidek W, Junker R, Seedorf U, von Eckardstein A, Assmann G, Walter M. Activation of phosphatidylinositol-specific phospholipase C by HDL-associated lysosphingolipid. Involvement in mitogenesis but not in cholesterol efflux. Biochemistry 2000; 39:15199-207. [PMID: 11106499 DOI: 10.1021/bi001162a] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Our earlier studies demonstrated that high-density lipoproteins (HDLs) stimulate multiple signaling pathways, including activation of phosphatidylcholine-specific phospholipases C and D (PC-PLs) and phosphatidylinositol-specific phospholipase C (PI-PLC). However, only activation of PC-PLs was linked to the HDL-induced cholesterol efflux. In the study presented here, the role of HDL-induced PI-PLC activation was studied. In human skin fibroblasts, HDL potently induced PI-PLC as inferred from enhanced phosphatidylinositol bisphosphate (PtdInsP(2)) turnover and Ca(2+) mobilization. The major protein component of HDL, apo A-I, did not induce PtdInsP(2) turnover or Ca(2+) mobilization in these cells. Both HDL and apo A-I promoted cellular cholesterol efflux, whereas only HDL induced fibroblast proliferation. Inhibition of PI-PLC with U73122 or blocking intracellular Ca(2+) elevation with Ni(2+) or EGTA markedly reduced the extent of HDL-induced cell proliferation but had no effect on cholesterol efflux. In fibroblasts from patients with Tangier disease which are characterized by defective cholesterol efflux, neither HDL-induced PtdInsP(2) breakdown and Ca(2+) mobilization nor cell proliferation was impaired. HDL-induced fibroblast proliferation, PtdInsP(2) turnover, and Ca(2+) mobilization were fully mimicked by the lipid fraction isolated from HDL. Analysis of this fraction with high-performance liquid chromatography (HPLC) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS) revealed that the PI-PLC-inducing activity is identical with two bioactive lysosphingolipids, namely, lysosulfatide (LSF) and sphingosylphosphorylcholine (SPC). Like native HDL, LSF and SPC induced PtdInsP(2) turnover, Ca(2+) mobilization, and fibroblast proliferation. However, both compounds did not promote cholesterol efflux. In conclusion, two agonist activities are carried by HDL. Apo A-I stimulates phosphatidylcholine breakdown and thereby facilitates cholesterol efflux, whereas LSF and SPC trigger PI-PLC activation and thereby stimulate cell proliferation.
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Jankowski J, Schröter A, Tepel M, van der Giet M, Stephan N, Luo J, Zidek W, Schlüter H. Isolation and characterization of coenzyme A glutathione disulfide as a parathyroid-derived vasoconstrictive factor. Circulation 2000; 102:2548-52. [PMID: 11076831 DOI: 10.1161/01.cir.102.20.2548] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Coenzyme A glutathione disulfide (CoA-SSG) was recently isolated from bovine adrenal glands and was shown to be a renal vasoconstrictor. The identification of CoA-SSG in human parathyroid glands and its action on cultured vascular smooth muscle cells (VSMCs) are described here. METHODS AND RESULTS After purification to homogeneity by several chromatographic steps, CoA-SSG was identified by matrix-assisted laser desorption/ionization mass spectrometry and enzymatic analysis. The dose-dependent growth-stimulating effect of CoA-SSG on VSMCs, measured by the [(3)H]thymidine method, is characterized by a threshold of 10(-)(8) mol/L and a maximum effect of 10 micromol/L, increasing VSMC proliferation 254+/-21% above control. A dose of 10 micromol/L methylmalonyl-CoA and 10 micromol/L CoA increased the rate of proliferation of VSMCs only by 178+/-43% and 50+/-42% above control, respectively. Glutathione has no proliferative effect on VSMCs. The growth-stimulating effect of CoA-SSG (1 micromol/L) was decreased by the antagonists 3,7-dimethyl-1-propargylxanthine (DMPX; 11 micromol/L) (38% compared with CoA-SSG without antagonist) and pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid (PPADS; 10 micromol/L) (48% compared with CoA-SSG without antagonist; each P:<0. 05 versus control), indicating that the effect is mediated partly via A(2) and partly via P(2)Y(1) and/or P(2)Y(4) receptor. CONCLUSIONS CoA-SSG may play a regulatory role in VSMC growth as a progression factor and thereby could play an important role in development of hypertension.
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MESH Headings
- Acetates/chemistry
- Angiotensin II/agonists
- Animals
- Cell Division/drug effects
- Cells, Cultured
- Chromatography, High Pressure Liquid
- Chromatography, Ion Exchange
- Coenzyme A/chemistry
- Coenzyme A/isolation & purification
- Coenzyme A/pharmacology
- Disulfides/chemistry
- Disulfides/isolation & purification
- Disulfides/pharmacology
- Dose-Response Relationship, Drug
- Glutathione/metabolism
- Glutathione/pharmacology
- Humans
- Mercaptoethanol/chemistry
- Molecular Weight
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Parathyroid Glands/chemistry
- Parathyroid Glands/enzymology
- Purinergic P1 Receptor Antagonists
- Purinergic P2 Receptor Antagonists
- Pyridoxal Phosphate/analogs & derivatives
- Pyridoxal Phosphate/pharmacology
- Rats
- Rats, Inbred WKY
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
- Theobromine/analogs & derivatives
- Theobromine/pharmacology
- Vasoconstrictor Agents/chemistry
- Vasoconstrictor Agents/isolation & purification
- Vasoconstrictor Agents/pharmacology
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Sanner BM, Konermann M, Tepel M, Groetz J, Mummenhoff C, Zidek W. Platelet function in patients with obstructive sleep apnoea syndrome. Eur Respir J 2000; 16:648-52. [PMID: 11106207 DOI: 10.1034/j.1399-3003.2000.16d14.x] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Patients with obstructive sleep apnoea syndrome (OSAS) are subject to an increased cardiovascular morbidity including myocardial infarction and stroke. Platelets play an important role in the pathogenesis and triggering of acute cardiovascular syndromes. So far, the influence of OSAS on platelet function is not fully understood. Platelet aggregability to epinephrine, collagen, arachidonic acid, and adenosine diphosphate in vitro was measured in 17 consecutive male patients (53.0+/-2.1 yrs) with polysomnographically verified OSAS and compared with that of 15 male controls (50.1+/-3.6 yrs) at 20:00 h, 24:00 h, and 06:00 h. In addition, the long-term effects of continuous positive airway pressure (CPAP) therapy on platelet aggregability was assessed after 6 months. Platelet aggregation in vitro induced by epinephrine showed a slight increase overnight in the untreated OSAS patients (NS) whereas it decreased slightly (NS) in the controls and in the treated OSAS patients. Pretherapeutic platelet aggregability was significantly lowered by CPAP therapy both at 24:00 h (64.0+/-6.5 versus 55.3+/-6.7%, p<0.05) and at 06:00 h (64.1+/-6.5 versus 45.8+/-7.6%; p=0.01). Platelet aggregability during sleep in the controls resembled that found in patients with OSAS during CPAP therapy. The results suggest that obstructive sleep apnoea syndrome contributes, at least in part, to platelet dysfunction and that long-term continuous positive airway pressure treatment may reduce platelet aggregability.
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Henning BF, Tepel M, Graefe U, Zidek W. [Homocysteine and its metabolites in chronic renal insufficiency and the effect of a vitamin replacement]. MEDIZINISCHE KLINIK (MUNICH, GERMANY : 1983) 2000; 95:477-81. [PMID: 11028163 DOI: 10.1007/pl00002136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
BACKGROUND Hyperhomocysteinemia has been increasingly recognized as an important risk factor for elevated atherosclerotic vascular disease in chronic renal failure. We measured in patients with chronic renal failure homocysteine and metabolites of its 2 metabolic pathways, transulfuration (cystathionine, cysteine) and remethylation (methionine, methylmalonic acid, 2-methylcitric acid). PATIENTS AND METHODS Eleven patients on conservative treatment (creatinine clearance 10 to 30 ml/min) and 50 chronic uremic subjects on regular hemodialysis were included in the study. Twenty-two of the dialysis patients received daily oral multivitamin supplementation containing 10 mg vitamin B6, 6 micrograms vitamin B12, and 1 mg folic acid during the last year before the study started. RESULTS In the hemodialysis group homocysteine levels were higher compared with the patients on conservative treatment. Hemodialysis patients with additional vitamin supplementation showed significantly lower homocysteine levels than those without. The pattern of metabolites was different to these results: all metabolites were higher in hemodialysis patients, too (significant for cysteine and methionine), but vitamin supplementation failed to lower all metabolites. CONCLUSION Analysis of metabolites additional to homocysteine levels may help to understand different results in evaluation of atherosclerotic risk of hyperhomocysteinemia in chronic renal failure.
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Tepel M, Sanner BM, van der Giet M, Zidek W. Increased sodium-proton antiporter activity in patients with obstructive sleep apnoea. J Sleep Res 2000; 9:285-91. [PMID: 11012869 DOI: 10.1046/j.1365-2869.2000.00207.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Cytosolic pH (pH(i)) and the activity of the sodium-proton antiporter (Na(+)/H(+) antiporter) were measured in lymphocytes from 22 patients with obstructive sleep apnoea and from 24 age-matched healthy subjects (Controls). The cellular Na(+)/H(+) antiporter was measured spectrophotometrically using a pH-sensitive fluorescent dye after intracellular acidification using sodium propionate. Resting pHi was similar in lymphocytes from patients with obstructive sleep apnoea and from controls (7.36 +/- 0.20, n=22; vs. 7.35 +/- 0.19, n=24; mean +/- SD). The Na(+)/H(+) antiporter activity was significantly higher in patients with obstructive sleep apnoea than in controls (11.87 +/- 3.26 x 10(-3) pH(i)/s vs. 4.38 +/- 1.40 x 10(-3) pH(i)/s; P < 0. 0001). The apparent affinity of the Na+/H+ antiporter was not significantly different between the groups (6.90 +/- 0.23 vs. 6.87 +/- 0.20). In patients with obstructive sleep apnoea the activity of the Na(+)/H(+) antiporter remained stable during the night. The activity of the Na(+)/H(+) antiporter was 13.49 +/- 4.80 x 10(-3) pH(i)/s at 20.00 and 13.26 +/- 6.13 x 10(-3) pH(i)/s at 02.00. From the present results it is concluded that an increased cellular Na(+)/H(+) antiporter activity may be a genetic marker for patients who are predisposed to obstructive sleep apnoea.
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Walter M, Tepel M, Nofer JR, Neusser M, Assmann G, Zidek W. Involvement of phospholipase D in store-operated calcium influx in vascular smooth muscle cells. FEBS Lett 2000; 479:51-6. [PMID: 10940387 DOI: 10.1016/s0014-5793(00)01880-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In non-excitable cells, sustained intracellular Ca2+ increase critically depends on influx of extracellular Ca2+. Such Ca2+ influx is thought to occur by a 'store-operated' mechanism, i.e. the signal for Ca2+ entry is believed to result from the initial release of Ca2+ from inositol 1,4,5-trisphosphate-sensitive intracellular stores. Here we show that the depletion of cellular Ca2+ stores by thapsigargin or bradykinin is functionally linked to a phosphoinositide-specific phospholipase D (PLD) activity in cultured vascular smooth muscle cells (VSMC), and that phosphatidic acid formed via PLD enhances sustained calcium entry in this cell type. These results suggest a regulatory role for PLD in store-operated Ca2+ entry in VSMC.
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Tepel M, Echelmeyer M, Orie NN, Zidek W. Increased intracellular reactive oxygen species in patients with end-stage renal failure: effect of hemodialysis. Kidney Int 2000; 58:867-72. [PMID: 10916112 DOI: 10.1046/j.1523-1755.2000.00236.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Reactive oxygen species (ROS) have been implicated in various forms of cellular injury. ROS may cause cell damage and are involved in the pathophysiology of several diseases, including atherosclerosis and chronic inflammation. METHODS Disturbances of intracellular ROS levels were investigated in 28 patients with end-stage renal failure. The intracellular ROS levels were measured in lymphocytes before and after hemodialysis using biocompatible membranes and were compared with those from 11 patients with end-stage renal failure, not yet on renal replacement therapy, and 27 healthy control subjects. ROS levels were measured spectrophotometrically using the intracellular dye dichlorofluorescin diacetate. RESULTS The spontaneous production of ROS was significantly higher in lymphocytes from patients with end-stage renal failure compared with healthy control subjects (P < 0.01). The addition of 100 nmol/L phorbol-myristate-acetate (PMA) produced a significant increase of ROS, both in lymphocytes from patients with end-stage renal failure and healthy control subjects. The PMA-induced ROS increase was significantly higher in lymphocytes from patients with end-stage renal failure compared with healthy control subjects (P < 0.01). In patients with end-stage renal failure, not yet on renal replacement therapy, the PMA-induced ROS was also significantly higher compared with healthy control subjects. The PMA-induced ROS increases were significantly inhibited by catalase, but not by superoxide dismutase or the superoxide dismutase mimetic, tempol. PMA-induced ROS was significantly reduced by tyrphostin A51 in lymphocytes from patients with end-stage renal failure and from healthy control subjects (each P < 0.01), indicating the involvement of a tyrosine kinase-dependent pathway. In patients with end-stage renal failure, the spontaneous and the PMA-induced production of ROS was not significantly different before and after hemodialysis. CONCLUSIONS Regular hemodialysis sessions using biocompatible membranes have no effect on the elevated intracellular ROS in patients with end-stage renal failure.
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Tepel M, van der Giet M, Schwarzfeld C, Laufer U, Liermann D, Zidek W. Prevention of radiographic-contrast-agent-induced reductions in renal function by acetylcysteine. N Engl J Med 2000; 343:180-4. [PMID: 10900277 DOI: 10.1056/nejm200007203430304] [Citation(s) in RCA: 946] [Impact Index Per Article: 39.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Radiographic contrast agents can cause a reduction in renal function that may be due to reactive oxygen species. Whether the reduction can be prevented by the administration of antioxidants is unknown. METHODS We prospectively studied 83 patients with chronic renal insufficiency (mean [+/-SD] serum creatinine concentration, 2.4+/-1.3 mg per deciliter [216+/-116 micromol per liter]) who were undergoing computed tomography with a nonionic, low-osmolality contrast agent. Patients were randomly assigned either to receive the antioxidant acetylcysteine (600 mg orally twice daily) and 0.45 percent saline intravenously, before and after administration of the contrast agent, or to receive placebo and saline. RESULTS Ten of the 83 patients (12 percent) had an increase of at least 0.5 mg per deciliter (44 micromol per liter) in the serum creatinine concentration 48 hours after administration of the contrast agent: 1 of the 41 patients in the acetylcysteine group (2 percent) and 9 of the 42 patients in the control group (21 percent; P=0.01; relative risk, 0.1; 95 percent confidence interval, 0.02 to 0.9). In the acetylcysteine group, the mean serum creatinine concentration decreased significantly (P<0.001), from 2.5+/-1.3 to 2.1+/-1.3 mg per deciliter (220+/-118 to 186+/-112 micromol per liter) 48 hours after the administration of the contrast medium, whereas in the control group, the mean serum creatinine concentration increased nonsignificantly (P=0.18), from 2.4+/-1.3 to 2.6+/-1.5 mg per deciliter (212+/-114 to 226+/-133 micromol per liter) (P<0.001 for the comparison between groups). CONCLUSIONS Prophylactic oral administration of the antioxidant acetylcysteine, along with hydration, prevents the reduction in renal function induced by contrast agents in patients with chronic renal insufficiency.
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Tepel M, van der Giet M, Zidek W. [Progressive renal failure. Why blood pressure must now be monitored]. MMW Fortschr Med 2000; 142:42-4. [PMID: 10920669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Hypertension alone can lead to chronic nephrosclerosis and in addition promote the progressive worsening of renal function in various forms of renal disease, such as diabetic nephropathy, glomerular nephritis or interstitial nephritis. Thus, the treatment of chronic renal disease associated with reduced excretory function, requires not only general measures and a low-protein diet, but also intensified anti-hypertension treatment with diuretics or beta blockers. In a number of studies, progression or renal insufficiency has been shown to be slowed in particular through the use of angiotensin-converting enzyme inhibitors in patients with chronic renal failure.
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