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Biomedical subjects

F Marumo

Publications and source records attributed to F Marumo.

At least 343 records · Page 19Linked to original sources
PubMed1994

Hepatitis C virus after interferon treatment has the variation in the hypervariable region of envelope 2 gene.

There is a hypervariable region in the envelope 2 gene of the hepatitis C virus genome, whose heterogeneity in different hepatitis C virus isolates has been suggested to be a result of the immune selection of escape variants. To determine the role of hypervariable region variants in the mechanism of resistance to interferon observed in 75-80% of interferon-treated patients with chronic hepatitis C, hypervariable region sequences were compared before and after interferon treatment. Eight patients with chronic hepatitis C were treated with recombinant interferon-alpha-2b. DNA containing the hypervariable region was obtained by reverse transcription-polymerase chain reaction from serial plasma samples of each patient and directly sequenced without cloning to determine changes in the predominant sequence. In two patients, hepatitis C virus-RNA was eliminated by interferon treatment. In the remaining six patients, hepatitis C virus-RNA was not eradicated. The predominant hepatitis C virus which survived interferon treatment was the mutant hepatitis C virus with 3-19 out of 81 nucleotide substitutions in the hypervariable region, resulting in 2-14 out of 27 amino acid changes. Most of the nucleotide substitutions were nonsynonymous, indicating that there were positive selections for amino acid changes in the hypervariable region. The change rate was significantly higher in patients whose plasma hepatitis C virus-RNA was consistently detectable during and after interferon treatment than in patients whose plasma hepatitis C virus-RNA became undetectable during treatment and reappeared after the cessation of the treatment (4.23 +/- 0.43 vs 0.77 +/- 0.20 x 10(-1)/site/year, p < 0.01). This suggests that the evolution of the hypervariable region was associated with the effect of interferon treatment. These results suggest that hypervariable region variants play an important role in maintaining persistent infection during interferon treatment by evading host immune surveillance.

Adult↗
PubMed1994

Detection and quantification of hepatitis C virus RNA replication in the liver.

To investigate the correlation between the replication of hepatitis C virus in liver and the clinical and histopathological features, we detected and quantified plus and minus strands of HCV-RNA in plasma and in livers of patients with chronic hepatitis C by a quantitative polymerase chain reaction. RNA was extracted from the plasma and liver tissue of ten patients with biopsy-proven chronic hepatitis C. The plus and minus strands of HCV-RNA were detected by a strand-specific reverse transcription with either sense or anti-sense oligonucleotide primers deduced from the hepatitis C virus genome, and a standard HCV-RNA with an enzyme restriction site was used to quantify the amount of HCV-RNA. Both plus and minus strands of HCV-RNA were detected from the liver tissue of all patients included. The amount of plus-stranded HCV-RNA in the liver was 10 times higher than that of minus-stranded HCV-RNA. Plus-stranded HCV-RNA was detected in the plasma in all patients, while the minus strand was not detected in any patient. There was a weak correlation between the amount of both strands of HCV-RNA in the liver and that of the plus strand in plasma. There was no significant correlation between the amount of liver HCV-RNA and serum alanine transaminase and aspartate transaminase levels, or histopathological findings in the liver. The present method of detecting and quantifying liver HCV-RNA is simple and sensitive; it may be used to detect residual hepatitis C virus replication after the disappearance of plasma HCV-RNA in acute hepatitis or in chronic hepatitis after interferon treatment.

Adult↗
PubMed1994

Localization of cyclophilin A and cyclophilin C mRNA in murine kidney using RT-PCR.

Cyclosporin A (CsA), which is widely used as an immunosuppressant, has a nephrotoxic side effect. The mechanism of this nephrotoxicity is not well understood; however, recent studies suggest that cyclophilin (cyp) is responsible for mediating the immunosuppressive action of CsA through the interaction with the Ca(2+)- and calmodulin-dependent phosphatase, calcineurin. While cyp A mRNA is expressed ubiquitously, cyp C mRNA has been shown to be topically expressed, including in the kidney. We examined: (1) distribution of cyp A and cyp C mRNA in microdissected murine nephron segments, using a combination of reverse transcription and polymerase chain reaction (RT-PCR) techniques, and (2) the effect of CsA administration on cyp C mRNA expression in proximal convoluted tubule. Among the nephron segments examined, large signals for cyp C PCR product were detected in proximal convoluted tubule and proximal straight tubule. Our data showed that the distribution of cyp C mRNA was uneven, and it mainly existed in segments that are relatively sensitive to CsA toxicity. In contrast, cyp A mRNA was found to be distributed almost equally along the nephron segments examined. By CsA administration, the signal for cyp C mRNA PCR product was increased. These results suggest that cyp C may play some role in the renal tubular disorder observed in CsA nephrotoxicity.

Amino Acid Isomerases↗
PubMed1994

Effects of hyperosmolality on ANP-stimulated cGMP generation in rat inner medullary collecting duct.

The inner medullary collecting duct (IMCD) is a major target site of atrial natriuretic peptide (ANP) for diuresis and natriuresis, and it is in a hypertonic condition made by the renal countercurrent multiplication system. We investigated the effects of hyperosmolality on ANP-stimulated cGMP generation in IMCD and glomerulus. Hypertonic solutions (490 and 690 mOsm/kg.H2O) were made by adding NaCl or urea to isotonic solution (290 mOsm/kg.H2O). Hypertonicity of 490 mOsm/kg.H2O using NaCl reduced both ANP-stimulated guanylate cyclase activity (from 7.7 +/- 1.1 to 4.1 +/- 0.5 fmol/mm/5 min) and cGMP generation (from 1.35 +/- 0.18 to 0.48 +/- 0.20 fmol/mm/3 min) in IMCD. Hypertonicity of 690 mOsm/kg.H2O using NaCl did not further reduce ANP-stimulated cGMP generation in IMCD. Hypertonicity using urea also inhibited ANP-stimulated guanylate cyclase activity and cGMP generation in IMCD. On the other hand, hypertonicity using NaCl stimulated AVP-stimulated cAMP generation in IMCD, while hypertonicity using urea reduced it. In glomeruli, hyperosmolality of 490 mOsm/kg.H2O using NaCl also reduced ANP-stimulated cGMP generation, and hypertonicity of 690 mOsm/kg.H2O using NaCl further reduced it. In summary, hyperosmolality using NaCl and urea inhibited ANP-sensitive guanylate cyclase activity and cGMP generation both in IMCD and glomeruli. However, the mechanisms at work may be different between NaCl and urea.

Animals↗
PubMed1994

Fluctuation of hepatitis C virus quasispecies in persistent infection and interferon treatment revealed by single-strand conformation polymorphism analysis.

Hepatitis C virus (HCV) populations in vivo consist of heterogeneous mixtures of genetically different but closely related variants defined as a 'quasispecies'. The longitudinal fluctuation of HCV quasispecies populations in chronic hepatitis C has not been elucidated. Serial plasma samples were obtained from four patients with chronic hepatitis C (two patients without any treatment and two patients treated with interferon), and cDNA fragments containing the 5'-terminal region of the E2 gene of HCV were amplified from plasma RNA using PCR. Since conventional cloning of PCR products detects only a small part of the entire population, PCR products of each sample were separated by electrophoresis using single-strand conformation polymorphism (SSCP) analysis, which can distinguish DNA fragments of the same size as different electrophoretic bands depending on their sequence-specific conformation. Separated DNA fragments were recovered from SSCP bands in gels and their nucleotide sequences determined. SSCP electrophoresis separated PCR products into bands with different mobility. Sequence analysis of these bands confirmed that HCV populations in each patient are composed of quasispecies with different E2-hypervariable regions (HVR), which are known to contain antibody epitopes. Different patterns of variation in the HVR of quasispecies were observed in individual patients with different clinical features over time during chronic infection. Following interferon treatment, some quasispecies disappeared during the treatment and reappeared after the end of the treatment, whereas other quasispecies in the same patient remained during the treatment suggesting that the sensitivity to interferon is different among quasispecies.

Base Sequence↗
PubMed1994

Atrioventricular nodal physiology after slow pathway ablation.

The AV nodal physiology before and 1 week after "slow pathway potential" guided catheter ablation was examined in 32 patients with AV nodal reentrant tachycardia. A mean of 4.9 applications of radiofrequency energy eliminated AV nodal reentrant tachycardia in all patients. There were no significant differences in sinus cycle length (815 +/- 159 msec vs 813 +/- 162 msec; P = NS) and fast pathway conduction properties before and 1 week after ablation. Slow pathway conduction was completely eliminated in 10 (31%) (group I) of 32 patients after ablation. In the remaining 22 patients residual slow pathway conduction associated with one AV node echo was observed. In 15 patients (47%) (group II), the effective refractory period of the slow pathway showed a change of < 30 msec (265 +/- 51 vs 266 +/- 51 msec; P = NS), and in 7 patients (22%) (group III), a prolongation of more than 80 msec (247 +/- 56 vs 340 +/- 42 msec; P = 0.0001) before and 1 week after ablation. Minimal and maximal A2-H2 interval over the slow pathway in group II was not significantly changed (Min A2-H2: 241 +/- 37 vs 247 +/- 40 msec; P = NS, Max A2-H2: 346 +/- 79 vs 350 +/- 60 msec; P = NS), while a significant prolongation was measured in group III (Min A2-H2: 261 +/- 53 vs 373 +/- 107 msec; P < 0.01, Max A2-H2: 359 +/- 41 vs 427 +/- 63 msec; P < 0.05) before and after ablation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Phenotypic change in portal fibroblasts in biliary fibrosis.

Portal fibroblasts have been considered responsible for biliary fibrosis. Since lipocytes show differentiation toward myofibroblast-like cells in hepatic fibrogenesis, we studied whether similar differentiation of portal fibroblasts could be observed in biliary fibrosis. We examined rat livers after bile duct ligation by double immunofluorescent staining of alpha-smooth-muscle actin (alpha-smA) and desmin and also by electronmicroscopy. In the portal tract of normal livers, alpha-smA-positive cells were noted only in the vessel wall, whereas desmin-positive cells were occasionally seen in the connective tissue as well. With the development of biliary fibrosis, alpha-smA was remarkably expressed in the portal connective tissue, while desmin was seen in a small portion of alpha-smA-positive cells around proliferating bile ducts. In normal livers, portal fibroblasts presented quiescent features, such as a small Golgi complex and a few cisternal profiles of endoplasmic reticulum under electron microscopy. After 7 days of bile duct ligation, portal fibroblasts proliferated, were arrayed in multilayers, and were associated with collagen bundles. Some of these fibroblasts had numerous cytoskeletal components, and developed rough endoplasmic reticulum and a dense body. These data suggest that portal fibroblasts appear to differentiate toward myofibroblasts in biliary fibrosis.

Actins↗
PubMed1994

Regulation of inducible nitric oxide synthase gene by interleukin-1 beta in rat vascular endothelial cells.

To elucidate the regulation of endothelial inducible nitric oxide synthase (iNOS), we studied the effects of interleukin (IL)-1 beta on production of nitric oxide (NO) and expression of iNOS mRNA and iNOS protein in cultured rat aortic endothelial cells (ECs) by measurement of NO2-/NO3- (NOx) and Northern blot and Western blot analyses. Among several cytokines and bacterial lipopolysaccharide tested, IL-1 beta most effectively stimulated NOx production. IL-1 beta dose and time dependently stimulated NOx production. Northern blot analysis using cDNA for mouse liver iNOS as a probe showed that IL-1 beta induced expression of iNOS mRNA and stimulated NOx production in a dose- and time-dependent manner. Transforming growth factor (TGF)-beta and dexamethasone blocked the IL-1 beta-induced NOx production as well as expression of iNOS mRNA and protein. TGF-beta dose dependently inhibited the IL-1 beta-induced NOx production and iNOS mRNA expression. Northern blot analysis for the decay of the IL-1 beta-induced iNOS mRNA revealed the approximate half-life of 4 h. These data indicate that IL-1 beta induces iNOS gene expression and de novo synthesis of iNOS and subsequent NO generation in vascular endothelium and that TGF-beta and glucocorticoid block iNOS gene expression at the transcriptional level.

Amino Acid Oxidoreductases↗
PubMed1994

Glomerular endothelial cells in culture express and secrete vascular endothelial growth factor.

Vascular endothelial growth factor (VEGF) is a specific growth factor for endothelial cells, and its abundant expression has been reported in kidney glomeruli. In this study, we focused on glomerular endothelial cells (GEN) as a possible source of VEGF secretion and sought to uncover a potential autocrine role of VEGF for GEN. Ribonuclease protection assay demonstrated VEGF mRNA expression in cultured GEN, and 46-kDa VEGF protein was detected in the conditioned medium by immunoblot analysis using polyclonal antibody raised against the NH2-terminal portion of VEGF. Removal of fetal bovine serum (FBS) from the culture medium for 2 h decreased VEGF mRNA abundance, which was restored by the readdition of FBS (10%) within 2 h. The effect of FBS was completely abolished by protein kinase inhibitor H-7 (10 microM), suggesting that FBS-stimulated VEGF mRNA induction involves activation of protein kinases. The treatment of GEN with 10(-7) M 12-O-tetradecanoylphorbol-13-acetate (TPA) increased the VEGF mRNA abundance fivefold, supporting the idea that VEGF expression is regulated by protein kinase C. [3H]thymidine incorporation into GEN treated with TPA (10(-7) M) was inhibited by neutralizing antibody for VEGF. Thus VEGF was identified as an autocrine growth factor for GEN in vitro. Its physiological role might be the regulation of GEN proliferation, and the induction of VEGF expression by FBS and TPA suggests its involvement in the response of glomerular capillary endothelial cells to injury in certain pathophysiological states.

Animals↗
PubMed1994

PCR localization of C-type natriuretic peptide and B-type receptor mRNAs in rat nephron segments.

The present study was undertaken to investigate the presence of C-type natriuretic peptide (CNP) mRNA and its receptor, natriuretic peptide B-type receptor (ANPR-B) mRNA, in rat renal structures. The microlocalization of mRNAs coding for CNP and ANPR-B was carried out in the rat kidney, using an assay of reverse transcription and polymerase chain reaction (RT-PCR) in individual microdissected renal tubule segments, glomeruli, vasa recta bundle, and arcuate arteries. The PCR signal for CNP was detected in glomerulus, vasa recta bundle, and arcuate artery. The PCR product of ANPR-B was widely present in renal structures. Relatively large amounts of ANPR-B PCR product were detected in glomerulus, vasa recta bundle, arcuate artery, and distal nephron segments. A relatively high concentration of CNP (10(-7) M) stimulated guanosine 3',5'-cyclic monophosphate accumulation in glomerulus, medullary thick ascending limb, cortical collecting duct, and inner medullary collecting duct. Our data demonstrate that CNP can be produced locally in the glomerulus and renal vascular system and that ANPR-B is widely distributed in renal structures. Thus CNP may influence renal function and act in autocrine and paracrine fashions in the kidney.

Animals↗
PubMed1994

Distribution of kallikrein-binding protein mRNA in kidneys and difference between SHR and WKY rats.

We investigated kallikrein-binding protein (KBP) mRNA distribution in the kidney of Sprague-Dawley (SD) rats, spontaneously hypertensive rats (SHR), and Wistar-Kyoto strain (WKY) rats. Northern blot analysis revealed that KBP mRNA was located mainly in the medulla and with lower amounts in SHR than in WKY rats. KBP mRNA in microdissected nephron segments was detected by reverse transcription and polymerase chain reaction (RT-PCR) followed by Southern blot analysis. In SD rats, the most abundant signals were consistently found in inner medullary collecting duct (IMCD), with small amounts in outer medullary collecting duct, proximal convoluted tubule, and glomerulus. No signals were found in connecting tubule and cortical collecting duct. The nephron distribution of KBP mRNA was similar in WKY and SD rats. Only a small amount of signal was found, however, in IMCD of SHR. In conclusion, 1) KBP mRNA was predominantly distributed in the medullary segments of the distal nephron, downstream from the known kallikrein activity site in the collecting duct, and 2) KBP mRNA expression was significantly decreased in the kidney of SHR.

Animals↗
PubMed1994

Protein, cell, and LTB4 concentrations of lung edema fluid produced by high capillary pressures in rabbit.

We previously demonstrated disruptions of the pulmonary capillary endothelium and alveolar epithelium at transmural pressures (Ptm) of 52.5 cmH2O in rabbit by electron microscopy. In the present study, we determined the characteristics of the alveolar edema fluid in this condition by carrying out bronchoalveolar lavage after blood perfusion for 10 min at Ptm of 12.5 (low), 32.5 (intermediate), and 52.5 cmH2O (high). At low Ptm, where our previous studies showed no ultrastructural changes, the volume of alveolar fluid obtained by urea dilution was very small, and the concentrations of proteins, cells, and leukotriene B4 (LTB4) in the bronchoalveolar lavage fluid (BALF) were low. However, at high Ptm the volume of alveolar fluid and the concentrations of total protein and cells in the BALF were greatly increased. The amount of LTB4 in the BALF also increased substantially from 6.0 to 49.5 micrograms (P < 0.001). Intermediate changes were seen at intermediate Ptm. We concluded that exposing pulmonary capillaries to high Ptm results in a high-permeability form of edema. In addition, the presence of LTB4 suggests that chemical mediators are released, possibly as the result of exposure of the reactive capillary endothelial basement membrane, as demonstrated by electron microscopy.

Albumins↗
PubMed1994

Plasma thrombomodulin in primary glomerular disease and lupus glomerulonephritis.

Although thrombomodulin (TM) in circulating blood is regarded as an indicator of vascular endothelial disorders, blood TM levels are also known to be affected by renal dysfunction. We measured plasma TM levels in primary glomerular disease (PGD) and lupus glomerulonephritis (GN) with the EIA method, and assessed the extent to which renal dysfunction and endothelial disorders contribute to plasma TM levels in these diseases. The plasma TM/serum creatinine (TM/Cr) ratio was significantly higher in lupus GN patients than in PGD patients or normal controls. A significant positive correlation was found between plasma TM and serum Cr levels in both PGD and lupus GN patients, but the slope (A) of the regression line (TM = A.Cr+B) in lupus GN patients was significantly steeper than in PGD patients. We conclude that plasma TM levels are greatly influenced by renal dysfunction, but that not only renal dysfunction but endothelial disorders may be an important determinant of increased plasma TM levels in diseases such as lupus GN.

Adult↗
PubMed1994

Endothelin ETA receptor antagonist blocks cardiac hypertrophy provoked by hemodynamic overload.

BACKGROUND: We have recently shown that angiotensin II-induced hypertrophy of cultured rat cardiomyocytes was partially blocked by an endothelin (ET) receptor antagonist (BQ123) selective for the ETA subtype, suggesting the possible involvement of endogenous ET-1 in the mechanism of cardiac hypertrophy in vitro. In the present study, we studied the in vivo blockade effects of BQ123 on cardiac hypertrophy provoked by left ventricular overload with aortic banding in adult rats. METHODS AND RESULTS: Forty rats were divided into four groups: (1) sham-operated rats without BQ123 administration, (2) rats with aortic banding without BQ123 administration, (3) sham-operated rats with BQ123 administration, and (4) rats with aortic banding with BQ123 administration. BQ123 (250 micrograms/h) was administered continuously by an osmotic pump starting 24 hours before operation. BQ123 blocked increases in the ratio of left ventricular weight to body weight and in the diameter of cardiomyocytes provoked by aortic banding at 1 week, but those blockade actions were no longer observed at 2 weeks. Skeletal alpha-actin and atrial natriuretic peptide (ANP) mRNA in the left ventricle, transcriptional markers for cardiac hypertrophy, significantly increased in the rats with aortic banding at 1 week and 2 weeks. In the rats with BQ123 administration, despite the hemodynamic overload, skeletal alpha-actin and ANP mRNA in the left ventricle remained at the control levels at 1 week; however, those blockade actions were abolished at 2 weeks. Plasma ET-1 levels increased after aortic banding, peaking at 24 hours, then returned to the basal level at 4 days. Prepro-ET-1 mRNA levels in the left ventricle also increased 24 hours after aortic banding, then declined to the basal level at 4 days. CONCLUSIONS: These data suggest that endogenous ET-1 synthesized in the cardiovascular system plays a role in the mechanism of cardiac hypertrophy during the early phase of pressure overload in vivo.

Actins↗
PubMed1994

Induction of nitric oxide synthase gene by interleukin-1 beta in cultured rat cardiocytes.

BACKGROUND: Impaired myocardial contractility in septic shock is protracting, which may be caused by cytokine-induced nitric oxide (NO) synthesis in the heart. However, the cellular mechanism by which cytokines induce nitric oxide synthase (NOS) in cardiocytes remains obscure. METHODS AND RESULTS: We studied the effect of human recombinant interleukin-1 beta (IL-1 beta) on synthesis of NO2-/NO3- (NOx) and the expression of NOS mRNA and protein in cultured neonatal rat cardiocytes. IL-1 beta dose-dependently (0.1 to 10 ng/mL) stimulated NOx production as a function of time (6 to 48 hours). Northern blot analysis using complementary DNAs for rat brain-type constitutive (c) NOS and mouse macrophage-type inducible (i) NOS as probes showed that IL-1 beta induced expression of mRNA for iNOS but not for cNOS, starting after 6 hours and reaching a maximum after 48 hours in cardiocytes. IL-1 beta similarly induced iNOS mRNA expression in cultured adult rat cardiocytes in a time-dependent manner. Western blot analysis using specific antibody against the N-terminal fragment of mouse iNOS revealed the expression of 130-kD iNOS-like protein in IL-1 beta-treated cardiocytes. Northern blotting and immunocytochemical study revealed that IL-1 beta-induced iNOS mRNA and iNOS-like immunoreactivity were exclusively localized to cardiac myocytes but also to nonmyocytes, to a lesser extent. NG-mono-methyl-L-arginine, an NOS inhibitor, completely blocked the IL-1 beta-induced NOx production, whose effect was reversed by L-arginine but not by D-arginine. Dexamethasone inhibited the IL-1 beta-induced NOx production as well as iNOS mRNA expression. Cycloheximide and actinomycin D completely inhibited the IL-1 beta-induced NOx production and iNOS mRNA expression. Neither a calmodulin inhibitor (W-7), a protein kinase C inhibitor (calphostin C), nor a Ca2+ channel antagonist (nicardipine) showed any effect on the IL-1 beta-induced NOx production. CONCLUSIONS: These data demonstrate that IL-1 beta induces macrophage-type iNOS mRNA expression mainly by cardiac myocytes but also by nonmyocytes to a lesser extent, and subsequent de novo protein synthesis of iNOS leads to excessive local production of NO by cardiocytes.

Amino Acid Oxidoreductases↗
PubMed1994

Oxygen uptake kinetics are determined by cardiac function at onset of exercise rather than peak exercise in patients with prior myocardial infarction.

BACKGROUND: Resting cardiac function does not necessarily affect exercise capacity. However, to determine whether it affects early dynamics of oxygen uptake (VO2) during exercise, we measured VO2 during a constant work rate and during incremental exercise testing in patients with a history of myocardial infarction. VO2 kinetics and exercise capacity were compared between patients with relatively high left ventricular ejection fractions (LVEF > or = 35%, group 1) and those with lower ejection fractions (LVEF < 35%, group 2). METHODS AND RESULTS: Forty patients with a history of prior myocardial infarction (age, 57 +/- 10 years) were monitored during 6 minutes of moderate constant work rate testing (40 +/- 8 W) and during symptom-limited incremental exercise testing with a cycle ergometer. VO2 was calculated from respired gas analysis on a breath-by-breath basis. Cardiac output determinations were made with a computerized cadmium telluride detector every 10 seconds during exercise. The VO2 time constant during constant work rate exercise was slower in group 2 (58.0 +/- 7.6 seconds) compared with group 1 (45.8 +/- 10.5 seconds, P = .0002), indicating slower kinetics in group 2. The time constant for the rise in cardiac output during exercise was also slower in patients with lower EFs (63.0 +/- 12.8 versus 50.0 +/- 12.2 seconds). However, there were no differences in exercise capacity parameters, such as the VO2 or cardiac output at peak exercise, obtained during incremental exercise testing among the two groups. CONCLUSIONS: The prolonged time constant of VO2, which is primarily determined during early parts of exercise, reflects delayed cardiac output response in patients with severely impaired LV function. The time constant of VO2 during submaximal constant work rate exercise can be used as a sensitive and discriminant measure of impaired cardiac reserve in these patients.

Adult↗
PubMed1994

C-type natriuretic peptide upregulates vascular endothelin type B receptors.

Cultured rat vascular smooth muscle cells (VSMCs) possess receptors for potent vasoconstrictor endothelin-1 (ET-1) as well as potent vasodilator natriuretic peptides (atrial, brain, and C-type natriuretic peptides [ANP, BNP, and CNP, respectively]). However, little is known about molecular interactions between endothelin receptors and natriuretic peptides in VSMCs. To elucidate whether natriuretic peptides regulate vascular endothelin receptors, we studied the effects of three natriuretic peptides on the capacity of 125I-ET-1 binding and expression of endothelin type A (ETA) and type B (ETB) receptor mRNAs in cultured rat VSMCs. CNP (10(-6) mol/L) increased 125I-ET-1 binding capacity in a time-dependent manner (6 to 48 hours) and stimulated cyclic GMP (cGMP) generation in a dose-dependent manner (10(-8)) to 10(-6) mol/L). Pretreatment with CNP (10(-8) to 10(-6) mol/L) and 8-bromo-cGMP (10(-5) to 10(-3) mol/L) for 24 hours resulted in dose-dependent increases in 125I-ET-1 binding in VSMCs. The three natriuretic peptides at the highest concentration (10(-6) mol/L) increased 125I-ET-1 binding and stimulated cGMP generation with almost the same rank order of efficacy (CNP > BNP > ANP). Scatchard analysis of binding studies revealed that CNP (10(-6) mol/L) and 8-bromo-cGMP (10(-3) mol/L) increased vascular endothelin receptor number by 28% and 88%, respectively, without changing its affinity. Pretreatment with both CNP and 8-bromo-cGMP increased ET-1-stimulated inositol 1,4,5-trisphosphate formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗