Biomedical subjects

V Regitz-Zagrosek

Publications and source records attributed to V Regitz-Zagrosek.

At least 55 records · Page 3Linked to original sources

PubMed1997

Angiotensin receptor type 1 mRNA in human right ventricular endomyocardial biopsies: downregulation in heart failure.

OBJECTIVE: Atrial angiotensin II receptors type 1 (AT1) are downregulated in end-stage human heart failure at mRNA and protein level. The present study investigated whether AT1 ventricular mRNA content was reduced in myocardial biopsies from heart failure patients. METHODS: AT1 mRNA was quantitated in right ventricular endomyocardial biopsies from 16 patients with decreased left ventricular function (LVEF 36 +/- 3%) due to dilated cardiomyopathy (DCM) and in biopsies from 12 patients with suspected myocardial disease but normal cardiac function (LVEF 62 +/- 2%). Two biopsies per patient were pooled, RNA was extracted and reverse-transcribed after addition of an AT1 cRNA standard. AT1 standard and wild-type RNA were amplified with the same primers in the same PCR tube. The PCR products were hybridized to a microtiter plate and detected and quantitated by an ELISA system. Glyceraldehyde phosphate dehydrogenase (GAPDH) mRNA was determined in the same samples as AT1 mRNA. RESULTS: In the biopsies from 16 patients with heart failure, a 68% decrease in AT1 mRNA content was found in comparison with 12 controls (heart failure 94 +/- 15 AT1 mRNA copies/ng RNA; controls 297 +/- 45; P < 0.001). Relating AT1 mRNA content to GAPDH mRNA confirmed the specific decrease in AT1 mRNA (AT1/GAPDH: heart failure 1.3 +/- 0.15; controls 3.4 +/- 0.5; p < 0.002). The best correlation between AT1 mRNA content and clinical parameters was found for right ventricular ejection fraction (r = 0.59, P < 0.01). CONCLUSIONS: The quantitative RT-PCR procedure indicated a loss of ventricular AT1 mRNA in human heart failure which corresponds to the loss of AT1 protein described previously. It may underlie the decrease in AT1 protein expression in human heart failure.

Adult↗

PubMed1997

Protein kinase C-dependent regulation of the human AT1 promoter in vascular smooth muscle cells.

The expression level of angiotensin II (ANG II) type 1 receptors (AT1) determines the magnitude of ANG II signaling in vascular smooth muscle cells (VSMC). AT1 mRNA expression in cultured bovine VSMC increased twofold after 8 h of protein kinase C (PKC) activation with phorbol 12-myristate 13-acetate (PMA), whereas stimulation with forskolin did not alter the AT1 mRNA level. The expression of AT1 promoter/exon 1 [-513/+92 base pairs (bp)] luciferase constructs transfected into VSMC increased 2.4-fold with PMA stimulation. In-gel kinase assays demonstrated rapid phosphorylation of mitogen-activating protein kinases (MAPK) ERK1 and ERK2 by PMA. Electrophoretic gel mobility shift assays showed sequence-specific binding of nuclear proteins from PMA-activated VSMC, identified as activator protein 1 (AP-1) complex in competition assays, to a radiolabeled AT1-promoter fragment (-368/-399 bp). Recombinant AP-1 binds in a sequence-specific manner to the -386/-399-bp region. Site-specific mutagenesis destroying the AP-1 site, the adjacent polyoma enhancer activator 3 element, or both sites simultaneously indicated that both sites together are necessary and sufficient to control basal and PMA-induced activation of the human AT1 promoter in transfected VSMC. The capability of the phorbol ester PMA to activate the human AT1 promoter in VSMC via an AP-1 element suggests a prominent role for PKC/MAPK and Ets proteins in AT1 regulation.

Animals↗

PubMed1997

Angiotensin II-induced leukocyte adhesion on human coronary endothelial cells is mediated by E-selectin.

Clinical data suggest a link between the activation of the renin-angiotensin system and cardiovascular ischemic events. Leukocyte accumulation in the vessel wall is a hallmark of early atherosclerosis and plaque progression. E-Selectin, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) are adhesion molecules participating in mediating interactions between leukocytes and endothelial cells and have been found to be expressed in athero-sclerotic plaques. We investigated whether angiotensin II, the effector of the renin-angiotensin system, influences the endothelial expression of E-selectin, VCAM-1, and ICAM-1. In coronary endothelial cells derived from explanted human hearts, angiotensin II (10(-11) to 10(-5) mol/L) induced a concentration-dependent increase in E-selectin expression. The effect was measured by cell ELISA and duplex reverse-transcription polymerase chain reaction (RT-PCR) and reached its maximum at 10(-7) mol/L. Angiotensin II induced only a small increase in E-selectin expression in cardiac microvascular endothelial cells. VCAM-1 and ICAM-1 were not affected by angiotensin II stimulation. In addition, the effect of angiotensin II-induced E-selectin expression on leukocyte adhesion was quantified under flow conditions. Angiotensin II (10(-7) mol/L) increased leukocyte adhesion significantly to 67% of the maximal effect by tumor necrosis factor-alpha at a wall shear stress of 2 dyne/cm2. This adhesion was found to be E-selectin dependent, as demonstrated by blocking antibodies. The AT1-receptor antagonist DUP 753 significantly reduced E-selectin-dependent adhesion, whereas the AT2-receptor antagonist PD 123177 had no inhibitory effect. In addition, only AT1-receptor, but not AT2-receptor, mRNA could be detected by RT-PCR in coronary endothelial cells. Therefore, it is suggested that AT1 receptors mediate the effects of angiotensin II on E-selectin expression and leukocyte adhesion on coronary endothelial cells.

Angiotensin II↗

PubMed1997

Use of manganese in RT-PCR eliminates PCR artifacts resulting from DNase I digestion.

The precise quantification of rare mRNA copies from intronless genes by reverse transcription polymerase chain reaction (RT-PCR) requires the complete removal of genomic DNA because discrimination of cDNA and DNA amplification products by differing sizes of PCR products is not possible. Elimination of DNA is achieved by treating the RNA sample with RNase-free DNase I before RT-PCR. The lack of a PCR product from DNase-treated RNA samples before RT is usually accepted as a proof of efficient DNA destruction. However, this may vary depending on the metal cofactor used in the DNase I cleavage. Treating DNA-contaminated RNA samples with DNase I and magnesium as a cofactor creates a negative PCR control after digestion without further RT. Paradoxically, after additional RT-PCR, the original intron-containing DNA fragment size may be produced again. In the presence of manganese as cofactor, RT-created DNA fragments do not appear. This is because in the presence of manganese, DNase I cleaves both DNA strands at approximately the same site, yielding DNA fragments that are blunt-ended or that have protruding termini of only one or two nucleotides in length. However, overlapping fragments with the potential to recombine are created by DNase digestion with magnesium as cofactor. Because one cannot differentiate between a PCR signal produced by RNA and one produced by recombined DNA after DNase I digestion and RT, all such DNase I assays should be performed with manganese instead of magnesium.

Artifacts↗

PubMed1996

The construction of the World Wide Web-accessible myocardial two-dimensional gel electrophoresis protein database "HEART-2DPAGE": a practical approach.

The construction of the two-dimensional electrophoresis (2-DE) gel protein database "HEART-2DPAGE" for human heart proteins, accessible via the World Wide Web (WWW), is described. This database provides the opportunity to retrieve descriptive information interactively by mouse clicking on a protein spot within a 2-DE gel image or to retrieve the position of a protein if its protein name or a search expression is given. The realization of searching for proteins, the creation of clickable spots, marked by crosses or textual information, and interactive viewing opportunities are discussed from a software-oriented point of view. The database takes into account that some human heart proteins are chamber specific. Several Common Gateway Interface (CGI) scripts are described and some practical experience is discussed.

Computer Communication Networks↗

PubMed1996

Molecular biology of angiotensin receptors and their role in human cardiovascular disease.

The actions of angiotensin II in the cardiovascular system are transmitted by two known and possibly some unknown angiotensin receptor types. AT1 and AT2 both correspond to G-protein-coupled receptors with seven hydrophobic transmembrane domains, several N-glycosylation sites and a potential G-protein binding site. Cloning of coding regions and promoter sequences contributed to the understanding of receptor protein function and regulation. Angiotensin receptors with atypical binding properties for the known AT1- and AT2-specific ligands are expressed on human cardiac fibroblasts and in the human ulcrus. In several animal models, receptors with high affinity for angiotensin (1-7) have been described. AT1 stimulation is mediated by the generation of phospholipid-derived second messengers, activation of protein kinase C, the MAPkinase pathway and of immediate early genes. Recently, phosphorylation and dephosphorylation of tyrosine kinases have been associated with AT1- and AT2-mediated signal transduction. ATR are regulated by phosphorylation, internalization, modification of transcription rate and mRNA stability. Regulation is highly cell and organ specific and includes upregulation of ATR in some pathophysiological situations where the renin angiotensin system is activated. Whereas the function of AT1 in the cardiovascular system is relatively well established, there is little information regarding the role of AT2. Recent hypotheses suggest an antagonism between AT1 and AT2 at the signal transduction and the functional level. Transgenic animal models, particularly with targeted disruption of the AT1 and AT2 genes, suggest the contribution of both genes to blood pressure regulation. Genetic polymorphisms have been described in the AT1 and AT2 gene or neighbored regions and are used to analyze the association between gene defects and cardiovascular diseases. AT1 antagonists are now being introduced into the treatment of hypertension and potentially heart failure, and more interesting pharmacological developments are expected from the ongoing basic studies.

Angiotensin I↗

PubMed1996

Reduced atrial angiotensin receptor type 1 mRNA content in end-stage human heart failure: assessment by a novel quantitative PCR-ELISA technique.

The number of atrial angiotensin II binding sites is reduced in end-stage human heart failure. The goals of our study were the development of a quantitative polymerase chain reaction for angiotensin II receptor type 1 mRNA to determine the angiotensin receptor type 1 (AT1) mRNA content in the atria of patients with end-stage heart failure. We established a quantitative PCR based on coamplification of AT1 wild-type and an internal standard in the same PCR, followed by liquid-phase hybridization of PCR products in microtiter plates and quantitation by ELISA. Glyceraldehyde phosphate dehydrogenase mRNA in the same samples was used to relate the AT1 mRNA content to a stably expressed reference gene. Atrial samples from 11 patients with end-stage heart failure obtained at cardiac transplantation were compared with atrial samples from 11 patients with normal cardiac function undergoing routine cardiac surgery. A PCR/ELISA system with a variance of about 6% after reverse transcription and a linear measuring range was established. In the samples from 11 patients with end-stage heart failure a 58% decrease in AT1 mRNA content was found in comparison with 11 controls (heart failure: 185,680 +/- 196,912 AT1 mRNA copies/microgram RNA, controls: 440,555 +/- 268,456, P < 0.02). When AT1 mRNA content was related to glyceraldehyde phosphate dehydrogenase mRNA, a 65% decrease was detected (AT1/glyceraldehyde phosphate dehydrogenase: heart failure: 4.84 +/- 5.18; controls: 13.74 +/- 7.77; P < 0.005). Standardization of PCR resulting in a low coefficient of variance, high reproducibility, and large sample capacity is possible using optimal internal standardization and the liquid-phase hybridization/ELISA system for detection. The optimized PCR procedure indicated downregulation of atrial AT1 in end-stage human heart failure, suggesting a reduced capacity of the atria to respond to angiotensin II stimulation in end-stage heart failure.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1996

Subtype 2 and atypical angiotensin receptors in the human heart.

Angiotensin receptors have been described in the human heart and are suspected to play a central role in remodeling after myocardial infarction and in cardiac hypertrophy. Two subtypes, AT1 and AT2, have so far been described in humans, with AT2 being the dominant subtype in human atria. We have now determined subtype numbers and distribution by binding in ventricular myocardium from patients with end-stage heart failure. We found about 50-80% of subtype AT2 in the right and left ventricles from patients with end-stage heart failure due to coronary artery disease and cardiomyopathy, indicating that AT2 is the dominant angiotensin receptor subtype in the whole human heart. To determine the cellular localization of angiotensin receptors in human myocardium in addition to the known localization on myocytes, smooth muscle cells and endothelial cells, we investigated cardiac fibroblasts. They express an angiotensin receptor with yet incompletely understood binding characteristics which is coupled to proliferation and DNA synthesis. As AT2 is the dominant angiotensin receptor subtype in human heart, we cloned the complete mRNA sequence by a rapid amplification of cDNA ends (RACE) procedure and thereafter the promoter sequence from a human genomic library. Once the sequence of the mRNA and thus exon 1 was obtained by the RACE-PCR, a probe was constructed for the most 5' region of exon 1 and used for screening of a human genomic DNA bank. After cutting of the positive clones with EcoR1 and Not1, a 4000 bp fragment hybridized with the probe and was further sequenced. A functional AT2 promoter, with > 90% homology with the mouse promoter and 35% homology with the human AT1 promoter containing numerous cis-acting sequences for basal (TFIID) and inducible (AP-1, PEA-3, CBF) transcription factors in the first 1000 bp was identified.

DNA↗

PubMed1996

Decreased expression of ventricular angiotensin receptor type 1 mRNA after human heart transplantation.

Myocardial angiotensin receptors of type 1 (AT1) are downregulated at the protein and mRNA levels in human heart failure. No data are available for the transplanted human heart, which frequently exhibits functional alterations. The aim of the present study was the quantitation of ventricular AT1 mRNA content in endomyocardial biopsies from patients after heart transplantation. For the determination of AT1 mRNA we used a novel quantitative reverse transcription polymerase chain reaction with low variance (6%) based on an internal AT1 cRNA standard, liquid-phase hybridization of polymerase chain reaction products in microtiter plates, and quantitation by enzyme-linked immunosorbent assay. Right ventricular biopsies from 16 patients after heart transplantation (left ventricular ejection fraction 67 +/- 7%) were compared with 12 patients with normal cardiac function (left ventricular ejection fraction 62 +/- 5%). A 46% lower AT1 mRNA content was found in biopsies from the 16 patients after heart transplantation than in the 12 controls (heart transplantation, 200 +/- 25 AT1 mRNA copies/ng RNA; controls, 368 +/- 50; P < 0.01). When AT1 mRNA content was related to the stably expressed GAPDH mRNA, a 49% decrease was detected (AT1/GAPDH: patients, 2.4 +/- 0.25; controls, 4.7 +/- 0.6; P < 0.006). No association between the extent of AT1 downregulation and clinical or hemodynamic variables was detected. In the human heart ventricular AT1 is downregulated after orthotopic heart transplantation. The decrease in AT1 mRNA is not associated with altered systolic function. This may partially reflect a loss of autonomic nerves and thus altered nervous control of the heart.

Adolescent↗

PubMed1996

Isolation and characterisation of human cardiac fibroblasts from explanted adult hearts.

Fibrosis makes an important contribution to the pathophysiological events leading to the development of heart failure in ischemic and hypertensive heart disease. Since cardiac fibroblasts are mainly responsible for the synthesis and deposition of the extracellular matrix, we have established a method for isolating and cultivating human cardiac fibroblasts from explanted human hearts. The cell yield was 2.14+/-0.25x10(6 )cells in five independent isolations and the cell purity was 95-97%, contaminating cells being vascular smooth muscle cells and pericytes. Cultured cells were studied with respect to growth properties, morphology and deposition of components of the extracellular matrix. Isolated cells displayed a differentiated phenotype, including the second passage in culture; they synthesised collagen I, III, IV, fibronectin, vitronectin, tenascin and chondroitin sulphate and expressed an atypical angiotensin receptor. This atypical angiotensin receptor internalised angiotensins II and III but not angiotensin IV in a time-dependent manner. Stimulation of the cells with angiotensins II and III but not with angiotensin IV resulted in a dose-dependent stimulation of DNA synthesis. Co-incubation with the subtype-specific receptor antagonists Losartan and PD 123317 did not prevent the stimulation of DNA synthesis. The further characterisation of this receptor should provide insights into the pathobiochemical events leading to heart failure in hypertension and ischemic heart disease.

Adult↗

PubMed1995

Regulation, chamber localization, and subtype distribution of angiotensin II receptors in human hearts.

BACKGROUND: To assess the chamber localization, subtype distribution, and regulation of human myocardial angiotensin II receptors in heart failure, we determined the binding of angiotensin II, Sar1Ile8-angiotensin II, and the subtype-specific antagonists Dup 753 (AT1-specific) and PD 123319 (AT2-specific) in atria from patients with normal (left ventricular ejection fraction > 55%) or moderately impaired (left ventricular ejection fraction 30% to 55%) cardiac function and in atria and ventricles from explanted end-stage failing hearts. Sarcolemmal and combined fractions, the latter including internalized receptors, were studied. In addition, AT1 mRNA content was analyzed by polymerase chain reaction after reverse transcription. METHODS AND RESULTS: The number of angiotensin II binding sites (Bmax) in sarcolemmal fractions was significantly reduced in explanted end-stage failing hearts in comparison with control subjects and moderate heart failure (Bmax 3.9 +/- 0.8 versus 11.2 +/- 1.7 and 9.6 +/- 0.8 fmol/mg protein, respectively). A comparable 65% reduction in receptor numbers was found in combined fractions from end-stage failing hearts, indicating that the loss of binding sites was not due to their internalization. The dissociation constants were comparable in sarcolemmal and combined fractions and in nonfailing and failing hearts, ranging from 0.5 +/- 0.2 to 1.2 +/- 0.5 nmol/L. In nonfailing hearts, 69 +/- 4% of binding sites were blocked by the subtype-2-specific inhibitor PD 123319 and were therefore classified as AT2; 33 +/- 5% were blocked by the subtype-1-specific inhibitor DUP 753 and thus classified as subtype 1. In explanted hearts, comparable ratios of 66 +/- 5% AT2 sites and 34 +/- 5% AT1 sites were found. AT1 cDNA amplification signals by polymerase chain reaction were reduced to about one third of the level in control subjects in end-stage failing hearts. CONCLUSIONS: Angiotensin II receptors in human myocardium are present in relatively low numbers, and AT2 is the predominant subtype. A significant loss of angiotensin II receptors occurs in end stage but not in moderate heart failure. The loss of receptors affects both subtypes to a comparable degree. The data suggest that the decrease in receptor density is due to a decrease in steady-state mRNA abundance.

Binding Sites↗

PubMed1995

Chamber-specific expression of human myocardial proteins detected by two-dimensional gel electrophoresis.

High resolution two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), followed by computer-assisted image analysis (PDQUEST) was used to screen atrial and ventricular protein patterns for quantitative and qualitative differences in protein expression. Myocardial proteins from left ventricular (LV) and right atrial (RA) samples from end-stage, failing explanted hearts and from a healthy donor heart (control) were separated by 2-D large gel electrophoresis. Ten RA versus ten LV gels from explanted dilated cardiomyopathic (DCM) hearts were analyzed for quantitative differences in their spot patterns. Of the 197 spots matched to every gel, 40 spots differed significantly in intensity between RA and LV for DCM patients. A larger number of atrial and ventricular gels (20 RA, 20 LV) from DCM patients and from a healthy donor heart (4 RA, 4 LV gels) were analyzed for qualitative differences in protein expression. Three protein spots (SSP 1120: M(r)/pI:20.5 kDa/4.6; SSP 1119: M(r)/pI:20.6 kDa/4.5; SSP 0117:M(r)/pI:20.7/ < 4.5) that are present in all RA gels for DCM patients are absent in all LV gels. Two protein spots (SSP 0112: M(r)/pI:17.2 kDa,/ < 4.4; SSP 0114:M(r)/pI:17.6 kDa/ < 4.4) occur only in all LV gels but not in the RA gels. These five qualitatively differing spots are identical in DCM patients and in the healthy donor heart. Some of the differing spots were internally sequenced and identified as myosin light chain isoforms (myosin light chain 2, atrial; myosin light chain 2, ventricular; myosin light chain 1, atrial) with the Protein Identification Resource (PIR) accession numbers A44451, S03708, A30881, respectively. Additionally, phosphoglycerate mutase (PIR: JQ0750) and ATP synthase alpha chain (PIR: S17193) were identified. Thus, quantitative and qualitative differences between atrial and ventricular protein patterns were identified by 2-D PAGE. A characteristic distribution of myosin light chains between atrial and ventricular human myocardium was found using our approach.

Amino Acid Sequence↗

PubMed1995

Angiotensin-converting enzyme inhibitors and beta-blockers in long-term treatment of dilated cardiomyopathy.

This double-blind, randomized, long-term study investigated the effects of the angiotensin-converting enzyme inhibitor enalapril and the beta-blocker metoprolol on clinical, hemodynamic, angiographic, and neurohormonal parameters in patients with dilated cardiomyopathy and moderate cardiac functional impairment (left ventricular ejection fraction [LVEF] 35% +/- 6%). After 12 months of treatment, a 12% reduction in 24-hour heart rate was observed in both groups (p < 0.05), whereas heart rate during exercise was reduced only in the metoprolol group. Echocardiographic fractional shortening increased (enalapril: 17% +/- 6% to 21% +/- 7%; metoprolol: 21% +/- 9% to 29% +/- 7%; both p < 0.05), as did the angiographic LVEF (enalapril: 35% +/- 7% to 43% +/- 12%, p = 0.1; metoprolol: 34% +/- 7% to 44% +/- 9%, p < 0.05), whereas ventricular volume decreased. Initially, both groups were comparable in terms of all parameters investigated. After 12 months fractional shortening was greater, and the heart rate at 50 W was lower in the beta-blocker group. At the doses used, the effect of the beta-blocker on dilated cardiomyopathy with moderate functional impairment was at least as great as that of the angiotensin-converting enzyme inhibitor.

Adrenergic beta-Antagonists↗

PubMed1995

Effects of angiotensin receptor antagonists in heart failure: clinical and experimental aspects.

In addition to inhibition of the circulating renin-angiotensin system, specific inhibition of the cardiac effects of angiotensin II (Ang II) represents an important therapeutic goal in the treatment of clinical heart failure. Subtype 1-specific Ang II receptor (AT1) antagonists have been developed to overcome potential limitations of angiotensin converting enzyme inhibitors, e.g. insufficient control of tissue Ang II production and bradykinin-related side effects. Clinical studies have demonstrated beneficial effects of AT1 antagonists. In a single-dose study, the AT1 antagonist losartan decreased the mean arterial pressure and pulmonary arterial pressure while increasing the cardiac index. Effects were dose dependent. Haemodynamic effects were greater with higher doses, but neurohormonal counter-regulation probably also increased, leading to relatively high levels of circulating Ang II with the 150-mg dose, A decrease in plasma levels of noradrenaline, atrial natriuretic factor, and aldosterone reached partial significance. Administration of multiple doses of losartan for 12 weeks also led to favourable haemodynamic and clinical results. Arterial blood pressure, pulmonary capillary wedge pressure, and systemic vascular resistance decreased. The neurohormonal effects of 12 weeks' administration of AT1 antagonists consisted in a decrease in plasma aldosterone concentrations. Whereas AT1 antagonists may counteract the effects of Ang II on the vasculature, and therefore are effective vasodilators, their direct myocardial effects are less clear. The subtype AT2, which represents the dominant, receptor in both healthy and failing human myocardium, is not blocked by AT1 inhibition. Angiotensin receptors on isolated human cardiac fibroblasts stimulate cellular proliferation via a yet undertermined receptor subtype. AT1 antagonists exert beneficial haemodynamic and neurohormonal effects in human heart failure. Their direct myocardial effects require further investigation.

Angiotensin Receptor Antagonists↗

PubMed1995

Tissue- and subtype-specific modulation of angiotensin II receptors by chronic treatment with cyclosporin A, angiotensin-converting enzyme inhibitors and AT1 antagonists.

We wished to determine whether chronic treatment of rats with cyclosporin A (CSA), an angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor antagonists modulates the angiotensin receptor density. In rats treated chronically with CSA, the vasoconstrictor response to angiotensin II (AII) is increased and this increase is modulated by ACEI and angiotensin receptor antagonists. Rats were treated for 6 weeks orally with CSA (15 mg/kg/day), the ACE inhibitor lisinopril (10 mg/kg/day), the angiotensin receptor antagonists DUP 753 (10 mg/kg/day), and D 8731 (10 mg/kg/day) and the combinations CSA + lisinopril, CSA + DUP 753, and CSA + D 8731. Olive oil was used as a control. The number of total AII receptors (Bmax) was determined by Scatchard analysis of [125I]Sar1 Ile8 AII binding in kidney, liver, adrenal cortex, and adrenal medulla. The receptor subtypes were analyzed with the specific antagonists DUP 753 (subtype 1) and PD 123319 (subtype 2). CSA upregulated angiotensin receptors in all organs studied. Lisinopril alone downregulated angiotensin receptors and abolished the effect of CSA in liver and adrenal cortex and medulla, but not in the kidney, where it had no effect. DUP 753 alone downregulated the angiotensin receptor subtype 1 in kidney, liver and adrenal cortex; its effect on the adrenal medulla in which 89% of angiotensin receptors are subtype 2, did not quite reach significance. The combination of DUP 753 and cyclosporin CSA abolished the CSA-induced increase in angiotensin receptor density in all four organs. The angiotensin receptor antagonists D 8731 downregulated the angiotensin receptors (subtype 1) in liver and kidney and upregulated angiotensin receptors (subtype 2) in the adrenal medulla.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1995

[Angiotensin receptors--organ and subtype specific regulation in cardiovascular diseases by modulation of the renin-angiotensin system. Studies of the rat model and in human myocardium].

So far, two angiotensin receptor subtypes, called AT1 and AT2, have been described in an animal model and in human. AT1 mediates almost all known effects of angiotensin II and its gene sequence and regulation is well studied. In contrast, only few data on function and regulation of AT2 are available. The complete mRNA sequence of AT2 has only recently been cloned and sequenced. The angiotensin receptors' receptor density and subtype distribution is organ specific. In the rat, lowest densities are found in the myocardium, followed by kidney, liver, adrenal medulla and cortex. The percentage of AT1 in the different organs amounts to 80, 85, 90, 57 and 10%. Angiotensin receptor subtypes have also been quantitated in human myocardium. There, the relatively unknown subtype AT2 dominates (67%). Myocardial receptor density is low, amounting to about 11 fmol/mg protein corresponding to 1/20-1/50 of the density of beta-adrenergic receptors. Angiotensin receptors in the human heart are present on cardiac fibroblasts and induce proliferation of these cells. Blockade of the renin angiotensin system by ACEI and AT1 antagonists in the rat downregulates angiotensin receptors in liver, kidney and adrenals to about 50% in an organ- and subtype specific manner, whereas cyclosporin A upregulates receptors twice. In end-stage human heart failure, but not in early stages, angiotensin receptors are downregulated to 1/3 of control values. Regulator mechanisms at transcriptional level have been elucidated by reporter gene assays; PMA, an activator of proteinkinase C, stimulates the transcription of the AT1 gene. The organ- and subtypespecific regulation of angiotensin receptors by pharmacological agents and/or cardiovascular diseases can contribute to the understanding of these drugs and of the pathophysiology of the corresponding diseases.

Animals↗

PubMed1994

Human cardiac fibroblasts express an angiotensin receptor with unusual binding characteristics which is coupled to cellular proliferation.

To assess the cellular localization of angiotensin receptors in human heart, we isolated human cardiac fibroblasts from explanted end-stage failing human hearts. As judged by an immunofluorescence assay, the isolated cells consisted of 96% of fibroblasts. Using receptor binding studies, we could identify a single angiotensin binding site on these cells, with a Kd of 0.6nM and a Bmax of 1.5 fmol/mg protein. Inhibiting concentrations 50 for Ang II and Ang I/II (1-7) were 40nM and 10nM, respectively. Stimulation with Ang II (100 nM) and Ang I/II (1-7) (100nM) led to cellular proliferation which could not be inhibited by Losartan or PD 123319. These results suggest that human cardiac fibroblasts express an as yet unknown angiotensin receptor-subtype.

Angiotensin II↗

PubMed1994

Protein composition of the human heart: the construction of a myocardial two-dimensional electrophoresis database.

Molecular changes occurring in myocardial diseases are not well understood. Proteins, as regulatory molecules, should play an important role in the etiology of these diseases. The method of two-dimensional electrophoresis (2-DE) allows the analysis of some thousand proteins with one experiment. An important prerequisite for this kind of investigation is the possibility of identifying the proteins separated by 2-DE. We resolve 3239 proteins of the human myocardium and tried to identify 33 proteins by amino acid analysis and microsequencing. Twenty proteins were identified by search for the protein-chemical data obtained in the Martinsried Institute Protein Sequence Database. Comparisons of 2-DE patterns of different size, which were obtained in different laboratories, were performed with the result that proteins identified on a 2-DE map of one laboratory can be assigned to spots of 2-DE maps produced by another laboratory. Our results show the usefulness of a myocardial 2-DE database; they can be used in different laboratories and make it possible to generate a collection of important human myocardial proteins in a 2-DE database for comparative studies worldwide.

Amino Acid Sequence↗