Abstract 12677: Impaired Cardiomyocyte Contractility to Angiotensin-(1-12) in a Humanized Angiotensinogen Model of Hypertension

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Yixi Liu ◽  
Heng Jie Cheng ◽  
Xiaoqiang Sun ◽  
Jing Cao ◽  
Zhe Chen ◽  
...  
Keyword(s):  
Contractile Function ◽  
Ang Ii ◽  
Transgenic Rats ◽  
Inotropic Effects ◽  
Cardiomyocyte Contractility ◽  
Inotropic Responses ◽  
Myocyte Contractility ◽  
Agt Gene ◽  
Rat Genome ◽  
Dependent Mechanism

Background: Angiotensin-(1-12) [Ang-(1-12)] is a chymase-dependent source for Angiotensin II (Ang II) inotropic activity that may be impaired in a model of sustained hypertension with high cardiac Ang II content due to insertion of the human angiotensinogen (AGT) gene in the rat genome. Accordingly, we evaluated the effects of Ang-(1-12) and Ang II on myocyte contractility and [Ca 2+ ] i regulation in 9 adult male transgenic rats expressing the human AGT gene [TGR(hAGT)L1623)] and 9 SD controls. Methods: We compared LV myocyte contraction, relaxation and [Ca 2+ ] i transient ([Ca 2+ ] iT ) responses to Ang-(1-12) (4x10 -6 M) and Ang II (10 -6 M) in freshly isolated LV myocytes. Results: Myocyte contraction (dL/dt max , 109.6 vs 127.9 μm/s), relaxation (dR/dt max , 95.3 vs 107.5 μm/s) and [Ca 2+ ] iT (0.15 vs 0.24) were depressed in TGR(hAGT)L1623 rats compared to SD controls. Moreover, cell contractile and [Ca 2+ ] iT responses following exposure to Ang-(1-12) or Ang II were markedly blunted. In SD myocytes, versus baseline, Ang II or Ang-(1-12) superfusion produced significant increases in dL/dt max [Ang II: 44% vs Ang-(1-12): 34%], dR/dt max (33% vs 26%) and [Ca 2+ ] iT (31% vs 25%). Importantly, the magnitude of the responses to the two agents in TGR(hAGT)L1623 myocytes was significantly reduced. Versus the changes in SD myocytes, Ang-(1-12) caused significantly less increases in dL/dt max (22%), dR/dt max (16%) and [Ca 2+ ] iT (15%) in TGR(hAGT)L1623 myocytes . Ang II also caused similar significantly attenuated increases in dL/dt max (27%), dR/dt max (25%) and [Ca 2+ ] iT (23%). The Ang-(1-12)-induced inotropic effects were completely prevented in the presence of the inhibitory cAMP analog, Rp-cAMPS (10 –4 M, 2 hours) in both SD and TGR(hAGT)L1623 myocytes, but were further augmented only intransgenic rats after incubation of myocytes with the G i inhibitor, pertussis toxin (PTX, 2 μg/ml, 36°C, 5 hours). Conclusions: Ang-(1-12) stimulates LV myocyte contractile function and [Ca 2+ ] iT in both SD and TGR(hAGT)L1623 rats. Furthermore, we now show that the blunted inotropic responses to Ang-(1-12) and Ang II in rats expressing the human AGT gene is mediated through a cAMP-dependent mechanism that is coupled to both stimulatory G and inhibitory PTX-sensitive G proteins.

Abstract MP04: Cardiac ACE2/Angiotensin-(1-7) in Rats Expressing Human Angiotensinogen Gene

Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Jasmina Varagic ◽  
Jessica VonCannon ◽  
Sarfaraz Ahmad ◽  
Michael Bader ◽  
Carlos M Ferrario
Keyword(s):  
Cardiac Hypertrophy ◽  
Cardiac Tissue ◽  
Male Rats ◽  
Ang Ii ◽  
Sprague Dawley ◽  
Transgenic Rats ◽  
Sd Rats ◽  
Agt Gene ◽  
Tissue Angiotensin

When compared to Sprague Dawley (SD) control rats, transgenic rats expressing the human angiotensinogen (AGT) gene [TGR(hAGT)L1623] exhibit hypertension associated with cardiac hypertrophy and higher cardiac tissue angiotensin (Ang) II. Whether the hypertension and cardiac hypertrophy in these rats expressing the human AGT are related to a non-canonical pathway for Ang II formation or suppression of the counter regulatory mechanism mediated by ACE2 and Ang-(1-7) has not been established. Consequently, cardiac peptides were determined by RIA in 9 [TGR(hAGT)L1623] and 11 SD male rats (17 weeks of age). ACE2 activities in homogenized heart tissues were determined by HPLC. Cardiac Ang II content was four times higher (37.05 ± 5.04 vs. 9.62 ± 0.93 fmol/mg protein; p <0.0001) while the Ang-(1-7) level increased only 1.3 times (18.02 ± 1.62 vs 13.37 ± 1.74 fmol/mg protein; p=0.06) in TGR(hAGT)L1623 rats when compared with SD rats. Although, the Ang II/Ang-(1-7) ratio was higher in transgenic rats harboring the human AGT gene (2.10 ± 0.27 vs 0.90 ± 0.19; p <0.005), ACE2 activities between these two strains of animals were not different (12.21 ± 0.76 vs. 10.80 ± 0.91 fmol/min/mg; p >0.05). Since human AGT protein is not cleaved by rat renin, our data continues to support the view that hypertension and cardiac hypertrophy in this transgenic strain are induced by activation of a non-renin mechanism rather than a primary suppression of the compensatory Ang II degrading pathway mediated by ACE2. Further studies are necessary to determine the role of enzymes affecting Ang-(1-7) metabolism in the observed inadequate balance between Ang II and Ang-(1-7).

Abstract 078: Functional Significance of the Chymase/Ang-(1-12) Pathway on Cardiomyocytes

Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Xiaowei Zhang ◽  
Tiankai Li ◽  
Sarfaraz Ahmad ◽  
Jasmina Varagic ◽  
Leanne Groban ◽  
...  
Keyword(s):  
Contractile Function ◽  
Peak Velocity ◽  
Cardiac Contractility ◽  
Calcium Transient ◽  
Cardiac Effect ◽  
Ang Ii ◽  
Adult Rat ◽  
Isolated Cardiac Myocytes ◽  
Direct Generation ◽  
Inotropic Responses

Angiotensin-(1-12) [Ang-(1-12)] functions in rodents and humans as a tissue substrate for the direct generation of Ang II via chymase. Since its direct cardiac effect have not been studied, the importance of this renin-independent mechanism for Ang II paracrine/intracrine actions in modulating cardiac contractility were determined in freshly isolated myocytes from 11 normal SD rats. Systolic amplitude (SA), peak velocity of shortening (dL/dtmax), the peak velocity of relengthening (dR/dtmax), and changes in the peak calcium transient ([Ca2+]i) were evaluated before and following exposure to Ang II (10-6 M), Ang-(1-12) delivered alone (range: 2x10-6 to 4x10-6 M) or after 1 h incubation with human recombinant chymase (10 μg protein/mL at 37°C). Both Ang II and the mixture of Ang-(1-12) with chymase elicited positive inotropic responses in freshly isolated cardiac myocytes associated with significant increases in peak systolic [Ca2+]i (Figure) while superfusion of Ang-(1-12) alone elicited an increase in dL/dtmax without significant changes in [Ca2+]i. The increases in contractility elicited by Ang II or the Ang-(1-12)/chymase mixture were abolished by prior exposure of the myocytes to losartan (10-5 M) or the chymase inhibitor chymostatin (8x10-5 M). We conclude that in single adult rat myocytes Ang-(1-12) stimulates contractile function through a chymase mediated action and by mechanisms that implicate a paracrine/intracrine activation of intracellular calcium.

Angiotensin II stimulates cardiac L-type Ca2+current by a Ca2+- and protein kinase C-dependent mechanism

2001 ◽  
Vol 280 (4) ◽  
pp. H1528-H1536 ◽  
Author(s):  
E. A. Aiello ◽  
H. E. Cingolani
Keyword(s):  
Protein Kinase C ◽  
Angiotensin Ii ◽  
Protein Kinase ◽  
Ang Ii ◽  
Patch Clamp Technique ◽  
Kinase C ◽  
Intracellular Ca ◽  
Inotropic Responses ◽  
Dependent Mechanism ◽  
In Cells

Angiotensin II (ANG II) evokes positive inotropic responses in various species. However, the effects of this peptide on L-type Ca2+ currents ( I Ca) are still controversial. We report in this study that the effects of ANG II on I Ca differ depending on the mode of patch-clamp technique used, standard whole cell (WC) or perforated patch (PP). No significant effects of ANG II (0.5 μM) were observed when WC in cells dialyzed with high EGTA was used. However, when the intracellular milieu was preserved using PP, ANG II induced a significant 77 ± 6% increase in I Ca (−2.2 ± 0.3 in control and −3.9 ± 0.6 pA/pF in ANG II, n = 8, P < 0.05). When WC was used in cells dialyzed with low Ca2+ buffer capacity (EGTA 0.1 mM), ANG II was able to induce an increase in I Ca (−3.5 ± 0.3 in control vs. −4.8 ± 0.4 pA/pF in ANG II, n = 13, P < 0.05). This increase was prevented when the cells were also dialyzed with the protein kinase C (PKC) inhibitor chelerythrine (50 μM) or calphostin C (1 μM). The above results allow us to conclude that strong intracellular Ca2+buffering prevents the physiological actions of ANG II on cardiac I Ca, which are also dependent on activation of PKC.

scholarly journals Neuronostatin inhibits cardiac contractile function via a protein kinase A- and JNK-dependent mechanism in murine hearts

2009 ◽  
Vol 297 (3) ◽  
pp. R682-R689 ◽  
Author(s):  
Yinan Hua ◽  
Heng Ma ◽  
Willis K. Samson ◽  
Jun Ren
Keyword(s):  
Contractile Function ◽  
Peptide Hormone ◽  
Left Ventricular ◽  
Maximal Velocity ◽  
Cardiac Contractile Function ◽  
Mechanical Responses ◽  
Cardiac Contractile ◽  
Short Term Exposure ◽  
The Impact ◽  
Dependent Mechanism

Neuronostatin, a newly identified peptide hormone sharing the same precursor with somatostatin, exerts multiple pharmacological effects in gastrointestinal tract, hypothalamus, and cerebellum. However, the cardiovascular effect of neuronostatin is unknown. The aim of this study was to elucidate the impact of neuronostatin on cardiac contractile function in murine hearts and isolated cardiomyocytes. Short-term exposure of neuronostatin depressed left ventricular developed pressure (LVDP), maximal velocity of pressure development (±dP/d t), and heart rate in Langendorff heart preparation. Consistently, neuronostatin inhibited peak shortening (PS) and maximal velocity of shortening/relengthening (±dL/d t) without affecting time-to-PS (TPS) and time-to-90% relengthening (TR90) in cardiomyocytes. The neuronostatin-elicited cardiomyocyte mechanical responses were mimicked by somatostatin, the other posttranslational product of preprosomatostatin. Furthermore, the neuronostatin-induced cardiomyocyte mechanical effects were ablated by the PKA inhibitor H89 (1 μM) and the Jun N-terminal kinase (JNK) inhibitor SP600125 (20 μM). The PKC inhibitor chelerythrine (1 μM) failed to alter neuronostatin-induced cardiomyocyte mechanical responses. To the contrary, chelerythrine, but not H89, abrogated somatostatin-induced cardiomyocyte contractile responses. Our results also showed enhanced c-fos and c-jun expression in response to neuronostatin exposure (0.5 to 2 h). Taken together, our data suggest that neuronostatin is a peptide hormone with overt cardiac depressant action. The neuronostatin-elicited cardiac contractile response appears to be mediated, at least in part, through a PKA- and/or JNK-dependent mechanism.

scholarly journals Computational modeling of Takotsubo cardiomyopathy: effect of spatially varying β-adrenergic stimulation in the rat left ventricle

2014 ◽  
Vol 307 (10) ◽  
pp. H1487-H1496 ◽  
Author(s):  
Sander Land ◽  
Steven A. Niederer ◽  
William E. Louch ◽  
Åsmund T. Røe ◽  
Jan Magnus Aronsen ◽  
...  
Keyword(s):  
Left Ventricle ◽  
Takotsubo Cardiomyopathy ◽  
Troponin I ◽  
Contractile Function ◽  
Single Cells ◽  
Apical Ballooning ◽  
Calcium Sensitivity ◽  
Takotsubo Syndrome ◽  
Adrenergic Stimulation ◽  
Inotropic Effects

In Takotsubo cardiomyopathy, the left ventricle shows apical ballooning combined with basal hypercontractility. Both clinical observations in humans and recent experimental work on isolated rat ventricular myocytes suggest the dominant mechanisms of this syndrome are related to acute catecholamine overload. However, relating observed differences in single cells to the capacity of such alterations to result in the extreme changes in ventricular shape seen in Takotsubo syndrome is difficult. By using a computational model of the rat left ventricle, we investigate which mechanisms can give rise to the typical shape of the ventricle observed in this syndrome. Three potential dominant mechanisms related to effects of β-adrenergic stimulation were considered: apical-basal variation of calcium transients due to differences in L-type and sarco(endo)plasmic reticulum Ca2+-ATPase activation, apical-basal variation of calcium sensitivity due to differences in troponin I phosphorylation, and apical-basal variation in maximal active tension due to, e.g., the negative inotropic effects of p38 MAPK. Furthermore, we investigated the interaction of these spatial variations in the presence of a failing Frank-Starling mechanism. We conclude that a large portion of the apex needs to be affected by severe changes in calcium regulation or contractile function to result in apical ballooning, and smooth linear variation from apex to base is unlikely to result in the typical ventricular shape observed in this syndrome. A failing Frank-Starling mechanism significantly increases apical ballooning at end systole and may be an important additional factor underpinning Takotsubo syndrome.

scholarly journals Positive Inotropic Effects of ATP Released via the Maxi-Anion Channel in Langendorff-Perfused Mouse Hearts Subjected to Ischemia-Reperfusion

2021 ◽  
Vol 9 ◽  
Author(s):  
Hiroshi Matsuura ◽  
Akiko Kojima ◽  
Yutaka Fukushima ◽  
Yu Xie ◽  
Xinya Mi ◽  
...  
Keyword(s):  
Contractile Function ◽  
Organic Anion ◽  
Left Ventricular ◽  
Transient Increase ◽  
Tyrode Solution ◽  
Inotropic Effects ◽  
Cl Channel ◽  
Short Period ◽  
Cl Channels ◽  
Normal Tyrode Solution

The organic anion transporter SLCO2A1 constitutes an essential core component of the ATP-conductive large-conductance anion (Maxi-Cl) channel. Our previous experiments using Langendorff-perfused mouse hearts showed that the Maxi-Cl channel contributes largely to the release of ATP into the coronary effluent observed during 10-min reperfusion following a short period (6 min) of oxygen-glucose deprivation. The present study examined the effect of endogenous ATP released via Maxi-Cl channels on the left ventricular contractile function of Langendorff-perfused mouse hearts, using a fluid-filled balloon connected to a pressure transducer. After the initial 30-min stabilization period, the heart was then perfused with oxygen-glucose-deprived Tyrode solution for 6 min, which was followed by a 10-min perfusion with oxygenated normal Tyrode solution in the absence and presence of an ATP-hydrolyzing enzyme, apyrase, and/or an adenosine A1 receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). In the absence of apyrase and DPCPX, the left ventricular developed pressure (LVDP) decreased from a baseline value of 72.3 ± 7.1 to 57.5 ± 5.5 mmHg (n = 4) at the end of 6-min perfusion with oxygen-glucose-deprived Tyrode solution, which was followed by a transient increase to 108.5 ± 16.5 mmHg during subsequent perfusion with oxygenated normal Tyrode solution. However, in the presence of apyrase and DPCPX, the LVDP decreased to the same degree during 6-min perfusion with oxygen-glucose-deprived Tyrode solution, but failed to exhibit a transient increase during a subsequent perfusion with oxygenated normal Tyrode solution. These results strongly suggest that endogenous ATP released through Maxi-Cl channels contributes to the development of transient positive inotropy observed during reperfusion after short-period hypoxia/ischemia in the heart.

112 Ang II Induces FAK Activation and Podocyte Migration Via a TRPC6-Dependent Mechanism

2011 ◽  
Vol 57 (4) ◽  
pp. B44
Author(s):  
Gentzon Hall ◽  
Guanghong Wu ◽  
Michelle Winn
Keyword(s):  
Ang Ii ◽  
Dependent Mechanism

Alterations in Blood Pressure and Heart Rate Variabililty in Transgenic Rats with Low Brain Angiotensinogen

Hypertension ◽  
2000 ◽  
Vol 36 (suppl_1) ◽  
pp. 727-727
Author(s):  
Ovidiu Baltatu ◽  
Ben J Janssen ◽  
Ralph Plehm ◽  
Detlev Ganten ◽  
Michael Bader
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Baroreflex Sensitivity ◽  
Circadian Variation ◽  
Ang Ii ◽  
Transgenic Rats ◽  
Short Term ◽  
Baroreflex Control ◽  
Sd Rats ◽  
The Brain

P191 The brain renin-angiotensin system (RAS) system may play a functional role in the long-term and short-term control of blood pressure (BPV) and heart rate variability (HRV). To study this we recorded in transgenic rats TGR(ASrAOGEN) with low brain angiotensinogen levels the 24-h variation of BP and HR during basal and hypertensive conditions, induced by a low-dose s.c. infusion of angiotensin II (Ang II, 100 ng/kg/min) for 7 days. Cardiovascular parameters were monitored by telemetry. Short-term BPV and HRV were evaluated by spectral analysis and as a measure of baroreflex sensitivity the transfer gain between the pressure and heart rate variations was calculated. During the Ang II infusion, in SD but not TGR(ASrAOGEN) rats, the 24-h rhythm of BP was inverted (5.8 ± 2 vs. -0.4 ± 1.8 mm Hg/group of day-night differences of BP, p< 0.05, respectively). In contrast, in both the SD and TGR(ASrAOGEN) rats, the 24-h HR rhythms remained unaltered and paralleled those of locomotor activity. The increase of systolic BP was significantly reduced in TGR(ASrAOGEN) in comparison to SD rats as previously described, while the HR was not altered in TGR(ASrAOGEN) nor in SD rats. The spectral index of baroreflex sensitivity (FFT gain between 0.3-0.6 Hz) was significantly higher in TGR(ASrAOGEN) than SD rats during control (0.71 ± 0.1 vs. 0.35 ± 0.06, p<0.05), but not during Ang II infusion (0.6 ± 0.07 vs. 0.4 ± 0.1, p>0.05). These results demonstrate that the brain RAS plays an important role in mediating the effects of Ang II on the circadian variation of BP. Furthermore these data are consistent with the view that the brain RAS modulates baroreflex control of HR in rats, with AII having an inhibitory role.

Renal vascular and tubulointerstitial inflammation and proliferation in Cyp1a1-Ren2 transgenic rats with inducible ANG II-dependent malignant hypertension

2007 ◽  
Vol 292 (6) ◽  
pp. F1858-F1866 ◽  
Author(s):  
Miguel L. Graciano ◽  
Cynthia R. Mouton ◽  
Matthew E. Patterson ◽  
Dale M. Seth ◽  
John J. Mullins ◽  
...  
Keyword(s):  
Cellular Proliferation ◽  
Morphological Changes ◽  
Periodic Acid ◽  
Cell Number ◽  
Malignant Hypertension ◽  
Nuclear Antigen ◽  
Ang Ii ◽  
Transgenic Rats ◽  
Periodic Acid Schiff ◽  
Proliferating Cell

Transgenic rats with inducible ANG II-dependent malignant hypertension [TGR(Cyp1a1Ren2)] were generated by inserting the mouse Ren2 renin gene into the genome of the rat. The present study was performed to assess renal morphological changes occurring during the development of ANG II-dependent malignant hypertension in these rats. Male Cyp1a1-Ren2 rats ( n = 10) were fed normal rat food containing indole-3-carbinol (I3C; 0.3%) for 10 days to induce malignant hypertension. Rats induced with I3C had higher mean arterial pressures (173 ± 9 vs. 112 ± 11 mmHg, P < 0.01) than noninduced normotensive rats ( n = 9). Glomerular damage was evaluated by determination of the glomerulosclerosis index (GSI) in tissue sections stained with periodic acid-Schiff. Kidneys of hypertensive rats had a higher GSI than normotensive rats (21.3 ± 5.6 vs. 3.5 ± 1.31 units). Quantitative analysis of macrophage ED-1-positive cells and proliferating cell nuclear antigen using immunohistochemistry demonstrated increased macrophage numbers in the renal interstitium (106.4 ± 11.4 vs. 58.7 ± 5.0 cells/mm2) and increased proliferating cell number in cortical tubules (37.8 ± 5.7 vs. 24.2 ± 2.1 cells/mm2), renal cortical vessels (2.2 ± 0.5 vs. 0.13 ± 0.07 cells/vessel), and the cortical interstitium (33.6 ± 5.7 vs. 4.2 ± 1.4 cells/mm2) of hypertensive rat kidneys. These findings demonstrate that the renal pathological changes that occur during the development of malignant hypertension in Cyp1a1-Ren2 rats are characterized by inflammation and cellular proliferation in cortical vessels and tubulointerstitium.

scholarly journals Effects of sprint training on contractility and [Ca2+]i transients in adult rat myocytes

2002 ◽  
Vol 93 (4) ◽  
pp. 1310-1317 ◽  
Author(s):  
Xue-Qian Zhang ◽  
Jianliang Song ◽  
Lois L. Carl ◽  
Weixing Shi ◽  
Anwer Qureshi ◽  
...  
Keyword(s):  
Contractile Function ◽  
Sprint Training ◽  
Cell Width ◽  
Western Blots ◽  
Adult Rat ◽  
Protein Levels ◽  
Intracellular Ca ◽  
Uptake Activity ◽  
Rat Myocytes ◽  
Myocyte Contractility

The effects of 6–8 wk of high-intensity sprint training (HIST) on rat myocyte contractility and intracellular Ca2+ concentration ([Ca2+]i) transients were investigated. Compared with sedentary (Sed) myocytes, HIST induced a modest (5%) but significant ( P < 0.0005) increase in cell length with no changes in cell width. In addition, the percentage of myosin heavy chain α-isoenzyme increased significantly ( P < 0.02) from 0.566 ± 0.077% in Sed rats to 0.871 ± 0.006% in HIST rats. At all three (0.6, 1.8, and 5 mM) extracellular Ca2+concentrations ([Ca2+]o) examined, maximal shortening amplitudes and maximal shortening velocities were significantly ( P < 0.0001) lower and half-times of relaxation were significantly ( P < 0.005) longer in HIST myocytes. HIST myocytes had significantly ( P < 0.0001) higher diastolic [Ca2+]i levels. Compared with Sed myocytes, systolic [Ca2+]ilevels in HIST myocytes were higher at 0.6 mM [Ca2+]o, similar at 1.8 mM [Ca2+]o, and lower at 5 mM [Ca2+]o. The amplitudes of [Ca2+]i transients were significantly ( P < 0.0001) lower in HIST myocytes. Half-times of [Ca2+]i transient decline, an estimate of sarcoplasmic reticulum (SR) Ca2+ uptake activity, were not different between Sed and HIST myocytes. Compared with Sed hearts, Western blots demonstrated a significant ( P < 0.03) threefold decrease in Na+/Ca2+ exchanger, but SR Ca2+-ATPase and calsequestrin protein levels were unchanged in HIST hearts. We conclude that HIST effected diminished myocyte contractile function and [Ca2+]itransient amplitudes under the conditions studied. We speculate that downregulation of Na+/Ca2+ exchanger may partly account for the decreased contractility in HIST myocytes.

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