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Ferrario CM, VonCannon J, Jiao Y, Ahmad S, Bader M, Dell'Italia LJ, Groban L, Varagic J. Cardiac angiotensin-(1-12) expression and systemic hypertension in rats expressing the human angiotensinogen gene. Am J Physiol Heart Circ Physiol 2016; 310:H995-1002. [PMID: 26873967 DOI: 10.1152/ajpheart.00833.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 02/08/2016] [Indexed: 12/12/2022]
Abstract
Angiotensin-(1-12) [ANG-(1-12)] is processed into ANG II by chymase in rodent and human heart tissue. Differences in the amino acid sequence of rat and human ANG-(1-12) render the human angiotensinogen (hAGT) protein refractory to cleavage by renin. We used transgenic rats harboring the hAGT gene [TGR(hAGT)L1623] to assess the non-renin-dependent effects of increased hAGT expression on heart function and arterial pressure. Compared with Sprague-Dawley (SD) control rats (n= 11), male homozygous TGR(hAGT)L1623 (n= 9) demonstrated sustained daytime and nighttime hypertension associated with no changes in heart rate but increased heart rate lability. Increased heart weight/tibial length ratio and echocardiographic indexes of cardiac hypertrophy were associated with modest reduction of systolic function in hAGT rats. Robust human ANG-(1-12) immunofluorescence within myocytes of TGR(hAGT)L1623 rats was associated with a fourfold increase in cardiac ANG II content. Chymase enzymatic activity, using the rat or human ANG-(1-12) as a substrate, was not different in the cardiac tissue of SD and hAGT rats. Since both cardiac angiotensin-converting enzyme (ACE) and ACE2 activities were not different among the two strains, the changes in cardiac structure and function, blood pressure, and left ventricular ANG II content might be a product of an increased cardiac expression of ANG II generated through a non-renin-dependent mechanism. The data also underscore the existence in the rat of alternate enzymes capable of acting on hAGT protein. Homozygous transgenic rats expressing the hAGT gene represent a novel tool to investigate the contribution of human relevant renin-independent cardiac ANG II formation and function.
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Affiliation(s)
- Carlos M Ferrario
- Department of Surgery, Wake Forest School of Medicine, Winston Salem, North Carolina; Departments of Medicine-Nephrology and Physiology-Pharmacology, Wake Forest School of Medicine, Winston Salem, North Carolina
| | - Jessica VonCannon
- Department of Surgery, Wake Forest School of Medicine, Winston Salem, North Carolina; Hypertension and Vascular Research Center, Wake Forest School of Medicine, Winston Salem, North Carolina
| | - Yan Jiao
- Department of Surgery, Wake Forest School of Medicine, Winston Salem, North Carolina
| | - Sarfaraz Ahmad
- Hypertension and Vascular Research Center, Wake Forest School of Medicine, Winston Salem, North Carolina
| | - Michael Bader
- Max-Delbrück-Center for Molecular Medicine (MDC), Berlin, Germany
| | - Louis J Dell'Italia
- Division of Cardiovascular Disease, University of Alabama at Birmingham and Department of Veterans Affairs, Birmingham Veterans Affairs Medical Center, Birmingham, Alabama
| | - Leanne Groban
- Hypertension and Vascular Research Center, Wake Forest School of Medicine, Winston Salem, North Carolina; Department of Anesthesiology, Wake Forest School of Medicine, Winston Salem, North Carolina; and
| | - Jasmina Varagic
- Department of Surgery, Wake Forest School of Medicine, Winston Salem, North Carolina; Hypertension and Vascular Research Center, Wake Forest School of Medicine, Winston Salem, North Carolina; Departments of Medicine-Nephrology and Physiology-Pharmacology, Wake Forest School of Medicine, Winston Salem, North Carolina
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Bohlender J, Ganten D, Luft FC. Rats transgenic for human renin and human angiotensinogen as a model for gestational hypertension. J Am Soc Nephrol 2000; 11:2056-2061. [PMID: 11053481 DOI: 10.1681/asn.v11112056] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Animal models of gestational hypertension are problematic. A novel mouse model was described earlier. The dams in that study were transgenic for human angiotensinogen and the sires for human renin; human renin was expressed in and produced by the placenta. This model was adapted to the rat, which has greater utility in terms of chronic instrumentation and physiologic measurements. Female rats transgenic for human angiotensinogen were mated with rats transgenic for human renin. Telemetry BP increased on day 5 of pregnancy from 110/80 mmHg to as high as 180/140 mmHg, while heart rate increased slightly. The renin transgene was expressed in the placenta, which resulted in increased human plasma renin concentration from 0 to 937 +/- 800 ng angiotensin I ml/h; the values returned to 0 after delivery. Female rats transgenic for human renin that were mated with male rats transgenic for human angiotensinogen in contrast exhibited a decrease in BP. In these rats, human angiotensinogen in plasma remained undetectable. Double transgenic offspring of these transgenic rats developed hypertension and end-organ damage, regardless of the source of the transgenes. The conclusion is that transgenic rats that bear human renin and angiotensinogen genes make an attractive model for gestational hypertension. The rat model will have greater utility than the mouse model.
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Affiliation(s)
- Jürgen Bohlender
- Franz Volhard Clinic, Berlin, Germany
- Max Delbrück Center, Medical Faculty of the Charié, Humboldt University of Berlin, Berlin, Germany
| | - Detlev Ganten
- Max Delbrück Center, Medical Faculty of the Charié, Humboldt University of Berlin, Berlin, Germany
- Department of Clinical Pharmacology, Klinikum Benjamin Franklin, Free University of Berlin, Berlin, Germany
| | - Friedrich C Luft
- Franz Volhard Clinic, Berlin, Germany
- Max Delbrück Center, Medical Faculty of the Charié, Humboldt University of Berlin, Berlin, Germany
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Abstract
The interplay of vasoactive peptide systems is an essential determinant of blood pressure regulation in mammals. While the endothelin and the renin-angiotensin systems raise blood pressure by inducing vasoconstriction and sodium retention, the kallikrein-kinin and the natriuretic-peptide systems reduce arterial pressure by eliciting vasodilatation and natriuresis. Transgenic technology has proven to be very useful for the functional analysis of vasoactive peptide systems. As an outstanding example, transgenic rats overexpressing the mouse Ren-2 renin gene in several tissues become extremely hypertensive. Several other transgenic rat and mouse strains with genetic modifications of components of the renin-angiotensin system have been developed in the past decade. Moreover, in recent years gene-targeting technology was employed to produce mouse strains lacking these proteins. The established animal models as well as the main insights gained by their analysis are summarized in this review.
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Affiliation(s)
- M Bader
- Max-Delbrück-Center for Molecular Medicine (MDC), Berlin-Buch, Germany.
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Bohlender J, Ménard J, Edling O, Ganten D, Luft FC. Mouse and rat plasma renin concentration and gene expression in (mRen2)27 transgenic rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:H1450-6. [PMID: 9612349 DOI: 10.1152/ajpheart.1998.274.5.h1450] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The (mRen2)27 transgenic rat [TGR(mRen2)27] is said to have low plasma levels of active renin. We used a direct radioimmunoassay (RIA) for mouse submaxillary renin, as well as an indirect enzyme-kinetic assay based on the generation of angiotensin I with modification of the pH optimum, to measure rat and mouse plasma renin activity (PRA), plasma renin concentration (PRC), and plasma prorenin in TGR before and after lisinopril. The relationship between rat PRC and % rat kidney extract was steepest at pH 6.0 and flat at pH 8.5, whereas the relationship between mouse PRC and purified mouse renin was steepest at pH 8.5 and flat at pH 6.0. Mouse PRC was highly correlated with direct RIA measurements (r = 0.93). PRA before lisinopril was little influenced by pH, whereas the increase with lisinopril was greatest at pH 6.5. PRC before lisinopril was fourfold higher at pH 8.5 compared with that at pH 6.0. Lisinopril increased both PRC values but reversed the pH dependency. Prorenin was fourfold higher at pH 8.5 compared with that at pH 6.0 and decreased slightly with lisinopril. Renal renin concentration was higher at pH 6.0 than at pH 8.5. With lisinopril, renal renin concentration increased at both pH values. Mouse PRC was not changed by lisinopril. Ribonuclease protection assay showed both rat and mouse renin gene expression in the kidney, which increased with lisinopril. Thus TGR have circulating active rat and mouse renin and prorenin. The notion that TGR are a "low renin" model should be revised.
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