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Speth RC, Carrera EJ, Bretón C, Linares A, Gonzalez-Reiley L, Swindle JD, Santos KL, Schadock I, Bader M, Karamyan VT. Distribution of non-AT1, non-AT2 binding of 125I-sarcosine1, isoleucine8 angiotensin II in neurolysin knockout mouse brains. PLoS One 2014; 9:e105762. [PMID: 25147932 PMCID: PMC4141804 DOI: 10.1371/journal.pone.0105762] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 06/13/2014] [Indexed: 11/18/2022] Open
Abstract
The recent identification of a novel binding site for angiotensin (Ang) II as the peptidase neurolysin (E.C. 3.4.24.16) has implications for the renin-angiotensin system (RAS). This report describes the distribution of specific binding of 125I-Sarcosine1, Isoleucine8 Ang II (125I-SI Ang II) in neurolysin knockout mouse brains compared to wild-type mouse brains using quantitative receptor autoradiography. In the presence of p-chloromercuribenzoic acid (PCMB), which unmasks the novel binding site, widespread distribution of specific (3 µM Ang II displaceable) 125I-SI Ang II binding in 32 mouse brain regions was observed. Highest levels of binding >700 fmol/g initial wet weight were seen in hypothalamic, thalamic and septal regions, while the lowest level of binding <300 fmol/g initial wet weight was in the mediolateral medulla. 125I-SI Ang II binding was substantially higher by an average of 85% in wild-type mouse brains compared to neurolysin knockout brains, suggesting the presence of an additional non-AT1, non-AT2, non-neurolysin Ang II binding site in the mouse brain. Binding of 125I-SI Ang II to neurolysin in the presence of PCMB was highest in hypothalamic and ventral cortical brain regions, but broadly distributed across all regions surveyed. Non-AT1, non-AT2, non-neurolysin binding was also highest in the hypothalamus but had a different distribution than neurolysin. There was a significant reduction in AT2 receptor binding in the neurolysin knockout brain and a trend towards decreased AT1 receptor binding. In the neurolysin knockout brains, the size of the lateral ventricles was increased by 56% and the size of the mid forebrain (−2.72 to +1.48 relative to Bregma) was increased by 12%. These results confirm the identity of neurolysin as a novel Ang II binding site, suggesting that neurolysin may play a significant role in opposing the pathophysiological actions of the brain RAS and influencing brain morphology.
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Affiliation(s)
- Robert C. Speth
- Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, Florida, United States of America
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, United States of America
- * E-mail:
| | - Eduardo J. Carrera
- Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, Florida, United States of America
- Farquhar College of Arts and Sciences, Nova Southeastern University, Fort Lauderdale, Florida, United States of America
| | - Catalina Bretón
- Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, Florida, United States of America
- Farquhar College of Arts and Sciences, Nova Southeastern University, Fort Lauderdale, Florida, United States of America
| | - Andrea Linares
- Farquhar College of Arts and Sciences, Nova Southeastern University, Fort Lauderdale, Florida, United States of America
| | - Luz Gonzalez-Reiley
- Farquhar College of Arts and Sciences, Nova Southeastern University, Fort Lauderdale, Florida, United States of America
| | - Jamala D. Swindle
- Farquhar College of Arts and Sciences, Nova Southeastern University, Fort Lauderdale, Florida, United States of America
| | - Kira L. Santos
- Farquhar College of Arts and Sciences, Nova Southeastern University, Fort Lauderdale, Florida, United States of America
- College of Dentistry, University of Florida, Gainesville, Florida, United States of America
| | - Ines Schadock
- Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
| | - Michael Bader
- Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
| | - Vardan T. Karamyan
- Department of Pharmaceutical Sciences, Texas Tech University Health Sciences Center, Amarillo, Texas, United States of America
- Center for Blood-Brain Barrier Research, Texas Tech University Health Sciences Center, Amarillo, Texas, United States of America
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Liu J, Yosten GLC, Ji H, Zhang D, Zheng W, Speth RC, Samson WK, Sandberg K. Selective inhibition of angiotensin receptor signaling through Erk1/2 pathway by a novel peptide. Am J Physiol Regul Integr Comp Physiol 2014; 306:R619-26. [PMID: 24523339 DOI: 10.1152/ajpregu.00562.2013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A seven-amino acid peptide (PEP7) is encoded within a short open reading frame within exon 2 (E2) in the 5'-leader sequence (5'LS) upstream of the rat ANG 1a-receptor (rAT1aR) mRNA. A chemically synthesized PEP7 markedly inhibited ANG II-induced Erk1/2 activation in cell culture by 62% compared with a scrambled PEP7 (sPEP7) [pErk1/2/Erk1/2 (AU): ANG II, 1.000 ± 0.0, ANG II+PEP7, 0.3812 ± 0.086, ANG II+sPEP7, 1.069 ± 0.18; n = 3]. Under these same conditions, PEP7 had no effect on ANG II-stimulated inositol-trisphosphate production. PEP7 also had no effect on epidermal growth factor- and phorbol methyl ester-induced Erk1/2 activation, suggesting PEP7 selectively inhibits AT1aR-mediated Erk1/2 signaling. PEP7 intracerebroventricularly inhibited ANG II-induced saline intake but had no effect on water intake in male and female rats, indicating PEP7 also selectively inhibits the ANG II-Erk1/2 pathway in vivo since saline drinking is Erk1/2-mediated, while water drinking is not. PEP7 inhibition of ANG II-induced saline ingestion was rapidly reversed by a subsequent intracerebroventricular injection of an oxytocin antagonist, suggesting when PEP7 blocks ANG II-stimulated Erk1/2 activation, animals no longer ingest saline to balance the continued water intake, due to the release of oxytocin and its subsequent inhibitory effects on saline drinking. PEP7 also attenuated ANG II-induced increases in arterial pressure by 35% compared with sPEP7 at the same dose. Thus, we have identified a novel peptide encoded within the rAT1aR E2 that selectively inhibits Erk1/2 activation, resulting in physiological consequences for sodium ingestion and arterial pressure that may have implications for treating sodium-sensitive diseases like hypertension and chronic kidney disease.
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Affiliation(s)
- Jun Liu
- Division of Nephrology and Hypertension, Department of Medicine, Georgetown University, Washington, D.C.
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Chhabra KH, Xia H, Pedersen KB, Speth RC, Lazartigues E. Pancreatic angiotensin-converting enzyme 2 improves glycemia in angiotensin II-infused mice. Am J Physiol Endocrinol Metab 2013; 304:E874-84. [PMID: 23462816 PMCID: PMC3625779 DOI: 10.1152/ajpendo.00490.2012] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An overactive renin-angiotensin system (RAS) is known to contribute to type 2 diabetes mellitus (T2DM). Although ACE2 overexpression has been shown to be protective against the overactive RAS, a role for pancreatic ACE2, particularly in the islets of Langerhans, in regulating glycemia in response to elevated angiotensin II (Ang II) levels remains to be elucidated. This study examined the role of endogenous pancreatic ACE2 and the impact of elevated Ang II levels on the enzyme's ability to alleviate hyperglycemia in an Ang II infusion mouse model. Male C57bl/6J mice were infused with Ang II or saline for a period of 14 days. On the 7th day of infusion, either an adenovirus encoding human ACE2 (Ad-hACE2) or a control adenovirus (Ad-eGFP) was injected into the mouse pancreas. After an additional 7-8 days, glycemia and plasma insulin levels as well as RAS components expression and oxidative stress were assessed. Ang II-infused mice exhibited hyperglycemia, hyperinsulinemia, and impaired glucose-stimulated insulin secretion from pancreatic islets compared with control mice. This phenotype was associated with decreased ACE2 expression and activity, increased Ang II type 1 receptor (AT1R) expression, and increased oxidative stress in the mouse pancreas. Ad-hACE2 treatment restored pancreatic ACE2 expression and compensatory activity against Ang II-mediated impaired glycemia, thus improving β-cell function. Our data suggest that decreased pancreatic ACE2 is a link between overactive RAS and impaired glycemia in T2DM. Moreover, maintenance of a normal endogenous ACE2 compensatory activity in the pancreas appears critical to avoid β-cell dysfunction, supporting a therapeutic potential for ACE2 in controlling diabetes resulting from an overactive RAS.
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Affiliation(s)
- Kavaljit H Chhabra
- Department of Pharmacology and Experimental Therapeutics and Cardiovascular Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
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Immunohistochemical Localization of AT1a, AT1b, and AT2 Angiotensin II Receptor Subtypes in the Rat Adrenal, Pituitary, and Brain with a Perspective Commentary. Int J Hypertens 2013; 2013:175428. [PMID: 23573410 PMCID: PMC3614054 DOI: 10.1155/2013/175428] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 02/01/2013] [Accepted: 02/05/2013] [Indexed: 11/17/2022] Open
Abstract
Angiotensin II increases blood pressure and stimulates thirst and sodium appetite in the brain. It also stimulates secretion of aldosterone from the adrenal zona glomerulosa and epinephrine from the adrenal medulla. The rat has 3 subtypes of angiotensin II receptors: AT1a, AT1b, and AT2. mRNAs for all three subtypes occur in the adrenal and brain. To immunohistochemically differentiate these receptor subtypes, rabbits were immunized with C-terminal fragments of these subtypes to generate receptor subtype-specific antibodies. Immunofluorescence revealed AT1a and AT2 receptors in adrenal zona glomerulosa and medulla. AT1b immunofluorescence was present in the zona glomerulosa, but not the medulla. Ultrastructural immunogold labeling for the AT1a receptor in glomerulosa and medullary cells localized it to plasma membrane, endocytic vesicles, multivesicular bodies, and the nucleus. AT1b and AT2, but not AT1a, immunofluorescence was observed in the anterior pituitary. Stellate cells were AT1b positive while ovoid cells were AT2 positive. In the brain, neurons were AT1a, AT1b, and AT2 positive, but glia was only AT1b positive. Highest levels of AT1a, AT1b, and AT2 receptor immunofluorescence were in the subfornical organ, median eminence, area postrema, paraventricular nucleus, and solitary tract nucleus. These studies complement those employing different techniques to characterize Ang II receptors.
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Rabey FM, Karamyan VT, Speth RC. Distribution of a novel binding site for angiotensins II and III in mouse tissues. REGULATORY PEPTIDES 2010; 162:5-11. [PMID: 20171994 PMCID: PMC7114337 DOI: 10.1016/j.regpep.2010.02.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Revised: 01/29/2010] [Accepted: 02/11/2010] [Indexed: 12/02/2022]
Abstract
A novel binding site for angiotensins II and III that is unmasked by parachloromercuribenzoate has been reported in rat, mouse and human brains. Initial studies of this binding site indicate that it is not expressed in the adrenal, liver or kidney of the rat and mouse. To determine if this binding site occurs in other mouse tissues, 8 tissues were assayed for expression of this binding site by radioligand binding assay and compared with the expression of this binding site in the forebrain. Particulate fractions of homogenates of testis, epididymis, seminal vesicles, heart, spleen, pancreas, lung, skeletal muscle, and forebrain were incubated with (125)I-sarcosine(1), isoleucine(8) angiotensin II in the presence or absence of 0.3mM parachloromercuribenzoate plus 10microM losartan and 10microM PD123319 (to saturate AT(1) and AT(2) receptors). Specific (3microM angiotensin II displaceable) high affinity binding occurred in the testis>forebrain>epididymis>spleen>pancreas>lung when parachloromercuribenzoate was present. Binding could not be reliably observed in heart, skeletal muscle and seminal vesicles. High affinity binding of (125)I-sarcosine(1), isoleucine(8) angiotensin II was observed in the absence of parachloromercuribenzoate in the pancreas on occasion. This suggests that this novel angiotensin binding site may have a functional role in these tissues.
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Affiliation(s)
- Felicia M. Rabey
- Department of Pharmacology, School of Pharmacy, University of Mississippi, University, MS 38677, USA
| | - Vardan T. Karamyan
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
| | - Robert C. Speth
- Department of Pharmacology, School of Pharmacy, University of Mississippi, University, MS 38677, USA,Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL 33328, USA,Corresponding author. Dept. Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, 3200 S. University Dr., Fort Lauderdale, FL 33328, USA. Tel.: +1 954 262 1330
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Mizuno CS, Chittiboyina AG, Shah FH, Patny A, Kurtz TW, Pershadsingh HA, Speth RC, Karamyan VT, Carvalho PB, Avery MA. Design, synthesis, and docking studies of novel benzimidazoles for the treatment of metabolic syndrome. J Med Chem 2010; 53:1076-85. [PMID: 20073471 DOI: 10.1021/jm901272d] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In addition to lowering blood pressure, telmisartan, an angiotensin (AT(1)) receptor blocker, has recently been shown to exert pleiotropic effects as a partial agonist of nuclear peroxisome proliferator-activated receptor gamma (PPAR gamma). On the basis of these findings and docking pose similarity between telmisartan and rosiglitazone in PPAR gamma active site, two classes of benzimidazole derivatives were designed and synthesized as dual PPAR gamma agonist/angiotensin II antagonists for the possible treatment of metabolic syndrome. Compound 4, a bisbenzimidazole derivative showed the best affinity for the AT(1) receptor with a K(i) = 13.4 nM, but it was devoid of PPAR gamma activity. On the other hand 9, a monobenzimidazole derivative, showed the highest activity in PPAR gamma transactivation assay (69% activation) with no affinity for the AT(1) receptor. Docking studies lead to the designing of a molecule with dual activity, 10, with moderate PPARgamma activity (29%) and affinity for the AT(1) receptor (K(i) = 2.5 microM).
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Affiliation(s)
- Cassia S Mizuno
- Department of Medicinal Chemistry, School of Pharmacy, The University of Mississippi, University, Mississippi 38677, USA
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Karamyan VT, Gadepalli R, Rimoldi JM, Speth RC. Brain AT1 Angiotensin Receptor Subtype Binding: Importance of Peptidase Inhibition for Identification of Angiotensin II as Its Endogenous Ligand. J Pharmacol Exp Ther 2009; 331:170-7. [DOI: 10.1124/jpet.109.157461] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Chittiboyina AG, Mizuno CS, Desai PV, Patny A, Kurtz TW, Pershadsingh HA, Speth RC, Karamyan V, Avery MA. Design, synthesis, and docking studies of novel telmisartan–glitazone hybrid analogs for the treatment of metabolic syndrome. Med Chem Res 2009. [DOI: 10.1007/s00044-008-9152-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Mizuno CS, Chittiboyina AG, Patny A, Kurtz TW, Pershadsingh HA, Speth RC, Karamyan VT, Avery MA. Design, synthesis, and docking studies of telmisartan analogs for the treatment of metabolic syndrome. Med Chem Res 2009. [DOI: 10.1007/s00044-008-9153-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Karamyan VT, Gembardt F, Rabey FM, Walther T, Speth RC. Characterization of the brain-specific non-AT(1), non-AT(2) angiotensin binding site in the mouse. Eur J Pharmacol 2008; 590:87-92. [PMID: 18571643 DOI: 10.1016/j.ejphar.2008.05.035] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Revised: 05/21/2008] [Accepted: 05/22/2008] [Indexed: 11/18/2022]
Abstract
In the present study the existence of a non-AT(1), non-AT(2) angiotensin (Ang) binding site unmasked by the organomercurial protease inhibitor p-chloromercuribenzoate (PCMB) was demonstrated in mouse brain membranes, consistent with observations previously reported in the rat (Karamyan and Speth, 2007b). The pharmacological specificity of the non-AT(1), non-AT(2) angiotensin binding site was similar to the rat brain: Sar(1)-Ile(8)-Ang II > Ang III >or= Ang II > Ang I> p-aminophenylalanine(6) Ang II> CGP42112 >> Ang IV > Ang 1-7 congruent with shorter angiotensin fragments. Neurotensin, bradykinin, and luteinizing hormone-releasing hormone showed K(i) values >10 microM, while substance P and VIP had K(i) values of approximately 2 microM. The non-AT(1), non-AT(2) angiotensin binding site was not present in adrenal, liver or kidney. Subcellular fractionation showed a higher density of [(125)I]Ang II binding in plasma membrane (P2) fractions of cerebral cortex and hypothalamus relative to debris (P1) fractions. The binding site is present in the brains of mice in which the AT(1a), AT(1b), AT(2), Mas, and neprilysin (EC 3.4.24.11, neutral endopeptidase) was knocked out confirming that the binding site is not a heretofore described angiotensin receptor or neprilysin. These observations confirm that this novel Ang binding site is distinct from classical AT(1), AT(2), AT(4) and Ang 1-7 receptors while retaining a high specificity for angiotensins that act on the known angiotensin receptors. Whether this binding site functions as a novel receptor for angiotensins or a specific angiotensinase with variable functionality at different redox states will require further study.
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Affiliation(s)
- Vardan T Karamyan
- Department of Pharmacology, School of Pharmacy, University of Mississippi, University, MS 38677, United States
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Karamyan VT, Speth RC. Identification of a novel non-AT1, non-AT2 angiotensin binding site in the rat brain. Brain Res 2007; 1143:83-91. [PMID: 17306233 DOI: 10.1016/j.brainres.2007.01.051] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Revised: 01/09/2007] [Accepted: 01/18/2007] [Indexed: 11/24/2022]
Abstract
Efforts to protect radiolabeled angiotensins from metabolism during receptor binding assays date back more than 30 years. However, this continues to be a problem. This study focused on the effects of a protease inhibitor, p-chloromercuribenzoate (PCMB), on the binding of (125)I-Ang II to rat brain membranes. Addition of PCMB to the incubation medium revealed a high affinity binding site for (125)I-Ang II in brain membranes (K(d)=1-4 nM) with a greater amount of binding than revealed in previous studies of brain Ang II receptors. Further characterization of this binding, revealed it to be insensitive to inhibition by losartan (an AT(1) receptor antagonist) and PD123319 (an AT(2) receptor antagonist). This non-AT1, non-AT2 binding site was not present in liver or adrenal membranes. It was activated by a limited range of concentrations of PCMB, with maximal activation at 0.3-1 mM. This binding site was equally abundant in cerebral cortex (a brain region with few Ang II receptors) and the hypothalamus (a brain region with abundant Ang II receptors). The binding site was also present in mouse brain, but not mouse liver. The binding site shows high affinity for Ang I, Ang II and Ang III (K(i) approximately 40-100 nM), but lesser affinity for smaller angiotensin fragments and other neuropeptides. This binding site shares some characteristics with the liver cytosolic Ang II binding proteins, later identified as endopeptidases EC 3.4.24.15 and/or EC 3.4.24.16. However, some unique characteristics of this non-AT1, non-AT2 binding site suggest that it may be a novel angiotensin binding substance.
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Affiliation(s)
- Vardan T Karamyan
- Department of Pharmacology and Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS 38677, USA
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Akhavan MM, Ebrahimi SA, Mahmoudian M. A non-radioactive method for angiotensin II receptor binding studies using the rat liver. J Pharmacol Toxicol Methods 2006; 53:206-14. [PMID: 16165374 DOI: 10.1016/j.vascn.2005.08.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Accepted: 08/16/2005] [Indexed: 10/25/2022]
Abstract
INTRODUCTION A new non-radioactive method based on competitive ELISA has been developed for binding studies on angiotensin II (Ang II) receptors. METHOD Rat liver membrane was used as the source of angiotensin receptors and FITC-angiotensin II (FITC-Ang II) was used as the labeled ligand with an affinity similar to unlabeled Ang II. The effects of different concentrations of Ang II, losartan, CGP-42112A and saralasin were studied on FITC-Ang II binding. RESULTS The Ki values for Ang II, losartan and CGP-42112A were calculated as 0.52+/-0.22 nM, 6+/-3 nM and 0.15+/-0.07 nM, respectively. Saralasin inhibited the binding of labeled ligand biphasically, revealing two different populations of Ang receptor with different affinities for saralasin. About 74% of the binding sites were more sensitive to saralasin with a Ki value of 0.32+/-0.04 nM while saralasin showed a Ki value of 2.7+/-0.8 nM for the remaining binding sites. DISCUSSION The competitive ELISA method developed in this work yields Ki values for angiotensin antagonists similar to those obtained by others using radiolabeled ligands. The simplicity of this method makes it a suitable alternative to radioligand studies for routine analysis of interaction of drugs with angiotensin receptors.
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Affiliation(s)
- Maziar Mohammad Akhavan
- Razi Institute for Drug Research, Iran University for Medical Sciences, Shaheed Hemmat Expressway, Tehran 14551, Iran
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